Species Recorded | Taxon | Scientific Name | Common Name | Records | Latest |
| alder fly, lacewing or snake fly | Chrysopa | a Chrysopa species (unidentified) | 7 | 2016 |
| alder fly, lacewing or snake fly | Chrysopa pallens | a green lacewing | 2 | 2009 |
| alder fly, lacewing or snake fly | Chrysopa perla | a green lacewing | 17 | 2016 |
| alder fly, lacewing or snake fly | Chrysoperla carnea group | a green lacewing | 52 | 2020 |
| alder fly, lacewing or snake fly | Chrysoperla lucasina | an insect - lacewing (Neuroptera) | 3 | 2013 |
| alder fly, lacewing or snake fly | Chrysopidae | a green lacewing (unidentified) | 13 | 2021 |
| alder fly, lacewing or snake fly | Chrysotropia ciliata | a green lacewing | 3 | 2014 |
| alder fly, lacewing or snake fly | Coniopterygidae | a dustywing (unidentified) | 2 | 2016 |
| alder fly, lacewing or snake fly | Coniopteryx (Coniopteryx) borealis | a white lacewing | 1 | 2015 |
| alder fly, lacewing or snake fly | Coniopteryx (Coniopteryx) tineiformis | a white lacewing | 1 | 1995 |
| alder fly, lacewing or snake fly | Cunctochrysa albolineata | an insect - lacewing (Neuroptera) | 2 | 2005 |
| algae or stonewort | Chara | a Chara stonewort (unidentified) | 52 | 2013 |
| algae or stonewort | Chara aculeolata | Hedgehog stonewort | 4 | 2009 |
| algae or stonewort | Chara contraria | Opposite Stonewort | 9 | 2015 |
| algae or stonewort | Chara globularis (sensu lato) | Fragile Stonewort | 18 | 2015 |
| algae or stonewort | Chara hispida (sensu lato) | Bristly Stonewort | 7 | 2000 |
| algae or stonewort | Chara virgata | Delicate Stonewort | 4 | 2003 |
| algae or stonewort | Chara virgata var. virgata | a Delicate Stonewort | 1 | 1990 |
| algae or stonewort | Chara vulgaris | Common Stonewort | 34 | 2016 |
| algae or stonewort | Chara vulgaris var. longibracteata | Common Stonewort var. longibracteata | 3 | 1999 |
| algae or stonewort | Chara vulgaris var. papillata | Common Stonewort var. papillata | 1 | 1917 |
| algae or stonewort | Chara vulgaris var. vulgaris | Common Stonewort var. vulgaris | 2 | 2016 |
| algae or stonewort | Charophyta | a Charophytes stonewort (unidentified) | 3 | 2004 |
| algae or stonewort | Chlorophyta/Xanthophyta sp. | a Chlorophyta/Xanthophyta filamentous alga (unidentified) | 36 | 2000 |
| algae or stonewort | Chondrus crispus | Carragheen | 2 | 1971 |
| algae or stonewort | Cladophora | Blanket Weed | 14 | 2018 |
| algae or stonewort | Cladophora glomerata | an alga | 21 | 2014 |
| algae or stonewort | Cladophora rupestris | an alga | 2 | 1938 |
| algae or stonewort | Closterium | a Closterium species (unidentified) | 1 | 2010 |
| algae or stonewort | Corallina officinalis | a red seaweed | 5 | 1990 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Caenacis inflexa | a chalcid wasp | 1 | 1998 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Calameuta filiformis | Reed Stem Borer | 5 | 2017 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Calameuta pallipes | a sawfly | 6 | 2013 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Caliadurgus fasciatellus | a spider-hunting wasp | 4 | 2006 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Caliroa annulipes | a sawfly | 3 | 2018 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Caliroa cerasi | a sawfly | 4 | 2021 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Callajoppa cirrogaster | an ichneumon wasp | 1 | 2020 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Callirhytis erythrocephala f. agamic | an insect - hymenopteran | 2 | 2001 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Campoletis annulata | an insect - hymenopteran | 2 | 2003 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Campoplex eudoniae | an insect - hymenopteran | 3 | 2008 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cecidostiba fungosa | an insect - hymenopteran | 26 | 2004 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cecidostiba semifascia | a chalcid wasp | 19 | 2003 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cephus pygmeus | Wheat Stem Borer | 4 | 2019 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cephus spinipes | a sawfly | 3 | 2006 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Ceratina cyanea | Blue Carpenter Bee | 5 | 2021 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cerceris arenaria | Sand Tailed Digger Wasp | 1 | 2000 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cerceris rybyensis | Ornate Tailed Digger Wasp | 19 | 2019 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Ceroptres clavicornis | a gall wasp | 1 | 2002 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chalcididae | a Chalcididae species (unidentified) | 15 | 2008 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chalcis sispes | a thick-legged chalcid wasp | 1 | 2002 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chelostoma campanularum | Harebell Carpenter Bee | 3 | 2018 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chelostoma florisomne | Sleepy Carpenter Bee | 4 | 2018 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chrysis | a Chrysis species (unidentified) | 6 | 2020 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chrysis angustula | a ruby-tailed wasp | 3 | 2001 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chrysis ignita | a ruby-tailed wasp | 17 | 2020 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chrysis ruddii | a ruby-tailed wasp | 1 | 2014 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chrysis vanlithi | a ruby-tailed wasp | 1 | 1987 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Chrysura radians | a rubytail wasp | 1 | 1987 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cidaphus atricillus | an ichneumon wasp | 1 | 1997 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cimbex femoratus | a clubhorned sawfly | 4 | 2021 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cimbex luteus | a clubhorned sawfly | 1 | 2021 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cirrospilus vittatus | a chalcid wasp | 1 | 2021 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cladius brullei | a sawfly | 2 | 2008 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cladius compressicornis | a sawfly | 1 | 2008 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cladius pectinicornis | a sawfly | 3 | 2001 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Claremontia brevicornis | a sawfly | 3 | 2021 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Claremontia tenuicornis | a sawfly | 3 | 2004 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cleptes semiauratus | a rubytail wasp | 2 | 2016 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Clinocentrus cunctator | a braconid wasp | 1 | 1995 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Clinocentrus exsertor | a braconid wasp | 2 | 1995 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Clistopyga incitator | an ichneumon wasp | 1 | 2019 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Coelinidea niger | a braconid wasp | 1 | 2003 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Coelioxys | a Coelioxys species (unidentified) | 6 | 2021 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Coelioxys elongata | a solitary bee | 4 | 2020 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Coelioxys inermis | a solitary bee | 4 | 2020 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Coelopisthia extenta | a chalcid wasp | 1 | 1997 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Colletes daviesanus | a solitary bee | 3 | 2020 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Colletes hederae | Ivy Bee | 64 | 2022 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Colletes similis | a solitary bee | 3 | 2009 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Colletes succinctus | a solitary bee | 6 | 2018 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cotesia glomerata | an insect - hymenopteran | 1 | 1979 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crabro cribrarius | Slender Bodied Digger Wasp | 2 | 2017 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus | a Crossocerus species (unidentified) | 3 | 2017 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus annulipes | a solitary wasp | 3 | 2006 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus cetratus | a solitary wasp | 4 | 2000 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus dimidiatus | Blunt Tailed Digger Wasp | 7 | 2001 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus distinguendus | a solitary wasp | 3 | 2009 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus elongatulus | Slender Digger Wasp | 13 | 2013 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus megacephalus | a solitary wasp | 13 | 2007 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus nigritus | a solitary wasp | 6 | 2002 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus ovalis | a solitary wasp | 2 | 2007 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus podagricus | a solitary wasp | 7 | 2008 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus quadrimaculatus | 4-spotted Digger Wasp | 4 | 2020 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus styrius | a solitary wasp | 2 | 2000 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus tarsatus | a solitary wasp | 1 | 1999 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus vagabundus | a solitary wasp | 1 | 1998 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus varus | a solitary wasp | 2 | 2000 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crossocerus walkeri | a solitary wasp | 1 | 2006 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Crypteffigies lanius | an ichneumon wasp | 1 | 1997 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cryptus armator | an insect - hymenopteran | 3 | 1997 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cyclolabus nigricollis | an ichneumon wasp | 1 | 2003 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cynipidae | a gall wasp (unidentified) | 11 | 2018 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cynips divisa | Red Currant Gall | 2 | 1999 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cynips longiventris | a gall wasp | 4 | 2006 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cynips longiventris f. agamic | an insect - hymenopteran | 6 | 2006 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cynips quercusfolii | Cherry Gall | 2 | 1999 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cyrtogaster vulgaris | a chalcid wasp | 2 | 2003 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cytisogaster genistae | a sawfly | 1 | 2000 |
| ant, bee, wasp, sawfly or ichneumon (and others) | Cytisogaster picta | a sawfly | 1 | 2004 |
| bacterium | Chroococcus | a Chroococcus species (unidentified) | 1 | 2010 |
| bacterium | Cyanophyta | a Cyanobacteria blue-green alga (unidentified) | 1 | 1998 |
| beetle | Caenoscelis ferruginea | a silken fungus beetle | 1 | 2015 |
| beetle | Cafius xantholoma | a rove beetle | 13 | 2019 |
| beetle | Calambus bipustulatus | a click beetle | 1 | 1932 |
| beetle | Calathus fuscipes | a ground beetle | 21 | 2020 |
| beetle | Calathus melanocephalus | a ground beetle | 14 | 2020 |
| beetle | Calathus melanocephalus agg. | a ground beetle | 3 | 2015 |
| beetle | Calathus mollis | a ground beetle | 2 | 2019 |
| beetle | Calathus rotundicollis | a ground beetle | 38 | 2021 |
| beetle | Calodromius spilotus | a ground beetle | 16 | 2021 |
| beetle | Calosirus terminatus | a weevil | 3 | 1968 |
| beetle | Calvia quattuordecimguttata | Cream-spot ladybird | 141 | 2022 |
| beetle | Cantharidae | a soldier beetle (unidentified) | 18 | 2017 |
| beetle | Cantharis | a Cantharis species (unidentified) | 7 | 2018 |
| beetle | Cantharis cryptica | a soldier beetle | 24 | 2018 |
| beetle | Cantharis decipiens | a soldier beetle | 63 | 2021 |
| beetle | Cantharis figurata | a soldier beetle | 3 | 2021 |
| beetle | Cantharis flavilabris | a soldier beetle | 65 | 2021 |
| beetle | Cantharis fusca | a soldier beetle | 14 | 2019 |
| beetle | Cantharis lateralis | a soldier beetle | 18 | 2017 |
| beetle | Cantharis livida | a soldier beetle | 28 | 2021 |
| beetle | Cantharis nigra (=thoracica) (red scutellum) | a soldier beetle | 1 | 1999 |
| beetle | Cantharis nigricans | a soldier beetle | 31 | 2020 |
| beetle | Cantharis obscura | a soldier beetle | 2 | 2017 |
| beetle | Cantharis pallida | a soldier beetle | 14 | 2018 |
| beetle | Cantharis pellucida | a soldier beetle | 18 | 2021 |
| beetle | Cantharis rufa | a soldier beetle | 29 | 2021 |
| beetle | Cantharis rustica | a soldier beetle | 154 | 2021 |
| beetle | Carabidae | a Carabidae species (unidentified) | 15 | 2017 |
| beetle | Carabus | a Carabus species (unidentified) | 2 | 2014 |
| beetle | Carabus granulatus | Granulated Ground Beetle | 24 | 2021 |
| beetle | Carabus monilis | Necklace Ground Beetle | 6 | 2018 |
| beetle | Carabus nemoralis | a ground beetle | 1 | 1999 |
| beetle | Carabus problematicus | Rough Violet Ground Beetle | 34 | 2021 |
| beetle | Carabus violaceus | Violet Ground Beetle | 55 | 2021 |
| beetle | Cardiophorus gramineus | a click beetle | 2 | 2009 |
| beetle | Carpelimus | a Carpelimus species (unidentified) | 1 | 2017 |
| beetle | Carpelimus bilineatus (sens. lat.) | a rove beetle | 1 | 1998 |
| beetle | Carpelimus elongatulus | a rove beetle | 2 | 2015 |
| beetle | Carpophilus marginellus | a pollen or sap beetle | 2 | 2017 |
| beetle | Cartodere bifasciata | a mould beetle | 10 | 2020 |
| beetle | Cartodere nodifer | a mould beetle | 50 | 2021 |
| beetle | Cassida flaveola | Pale Tortoise Beetle | 1 | 2001 |
| beetle | Cassida murraea | Fleabane Tortoise Beetle | 12 | 2021 |
| beetle | Cassida rubiginosa | Thistle Tortoise Beetle | 33 | 2021 |
| beetle | Cassida vibex | a leaf beetle | 13 | 2020 |
| beetle | Cassida viridis | Green Tortoise Beetle | 20 | 2021 |
| beetle | Cassida vittata | Borded Tortoise Beetle | 6 | 2019 |
| beetle | Catapion pubescens | a seed weevil | 1 | 1998 |
| beetle | Catapion seniculus | a seed weevil | 10 | 2010 |
| beetle | Cathormiocerus spinosus | a weevil | 4 | 1968 |
| beetle | Catops | a Catops species (unidentified) | 12 | 2020 |
| beetle | Catops chrysomeloides | a round fungus beetle | 5 | 2003 |
| beetle | Catops fuliginosus | a round fungus beetle | 56 | 2021 |
| beetle | Catops fuscus | a round fungus beetle | 8 | 2016 |
| beetle | Catops grandicollis | a round fungus beetle | 2 | 2015 |
| beetle | Catops kirbii | a round fungus beetle | 1 | 1978 |
| beetle | Catops morio | a round fungus beetle | 3 | 2021 |
| beetle | Catops nigricans | a round fungus beetle | 30 | 2021 |
| beetle | Catops nigrita | a round fungus beetle | 6 | 2017 |
| beetle | Catops tristis | a round fungus beetle | 26 | 2021 |
| beetle | Cephennium gallicum | a small ant-like beetle | 1 | 2008 |
| beetle | Cerambycidae | a Cerambycidae species (unidentified) | 1 | 2011 |
| beetle | Cerambycidae sp. or Nitidulidae sp. | a longhorn beetle (unidentified Cerambycidae sp. or Nitidulidae sp.) | 5 | 2012 |
| beetle | Ceratapion | a Ceratapion species (unidentified) | 1 | 1986 |
| beetle | Ceratapion carduorum | a seed weevil | 4 | 2018 |
| beetle | Ceratapion gibbirostre | a seed weevil | 10 | 2018 |
| beetle | Ceratapion onopordi | a seed weevil | 15 | 2017 |
| beetle | Cercyon | a Cercyon species (unidentified) | 2 | 2012 |
| beetle | Cercyon analis | a scavenger water beetle | 4 | 2017 |
| beetle | Cercyon bifenestratus | a scavenger water beetle | 1 | 2021 |
| beetle | Cercyon convexiusculus | a scavenger water beetle | 9 | 2012 |
| beetle | Cercyon depressus | a scavenger water beetle | 2 | 2017 |
| beetle | Cercyon haemorrhoidalis | a scavenger water beetle | 3 | 2021 |
| beetle | Cercyon impressus | a scavenger water beetle | 1 | 2009 |
| beetle | Cercyon laminatus | a scavenger water beetle | 2 | 2014 |
| beetle | Cercyon lateralis | a scavenger water beetle | 3 | 2021 |
| beetle | Cercyon littoralis | a scavenger water beetle | 6 | 2021 |
| beetle | Cercyon marinus | a scavenger water beetle | 3 | 2002 |
| beetle | Cercyon melanocephalus | a scavenger water beetle | 2 | 2016 |
| beetle | Cercyon obsoletus | an insect - beetle (Coleoptera) | 1 | 2002 |
| beetle | Cercyon pygmaeus | a scavenger water beetle | 4 | 2021 |
| beetle | Cercyon quisquilius | a scavenger water beetle | 5 | 2018 |
| beetle | Cercyon sternalis | a scavenger water beetle | 1 | 1999 |
| beetle | Cercyon terminatus | a scavenger water beetle | 2 | 1997 |
| beetle | Cercyon tristis | a scavenger water beetle | 3 | 1999 |
| beetle | Cercyon unipunctatus | a scavenger water beetle | 2 | 2016 |
| beetle | Cerylon ferrugineum | a cerylonid beetle | 5 | 2016 |
| beetle | Cerylon histeroides | a cerylonid beetle | 6 | 2021 |
| beetle | Cetonia aurata | Rose Chafer | 398 | 2022 |
| beetle | Ceutorhynchus | a Ceutorhynchus species (unidentified) | 2 | 2015 |
| beetle | Ceutorhynchus alliariae | a weevil | 1 | 1979 |
| beetle | Ceutorhynchus assimilis (sens. lat. (assimilis/obstrictus)) | Cabbage Gall Weevil | 6 | 2003 |
| beetle | Ceutorhynchus cochleariae | a weevil | 1 | 1983 |
| beetle | Ceutorhynchus contractus | Cabbage Leaf Weevil | 5 | 2015 |
| beetle | Ceutorhynchus erysimi | a weevil | 6 | 2008 |
| beetle | Ceutorhynchus hirtulus | a weevil | 2 | 2018 |
| beetle | Ceutorhynchus obstrictus | Cabbage Seed Weevil | 21 | 2019 |
| beetle | Ceutorhynchus pallidactylus | Cabbage Stem Weevil | 18 | 2020 |
| beetle | Ceutorhynchus pyrrhorhynchus | a weevil | 3 | 1978 |
| beetle | Ceutorhynchus typhae | a weevil | 5 | 2016 |
| beetle | Chaetocnema | a Chaetocnema species (unidentified) | 1 | 2020 |
| beetle | Chaetocnema concinna | Beet Flea Beetle | 27 | 2021 |
| beetle | Chaetocnema confusa | a leaf beetle | 3 | 2015 |
| beetle | Chaetocnema hortensis | a leaf beetle | 22 | 2021 |
| beetle | Chaetocnema sahlbergii | a leaf beetle | 5 | 2019 |
| beetle | Charagmus griseus | a weevil | 2 | 2019 |
| beetle | Chilocorus bipustulatus | a ladybird | 2 | 2021 |
| beetle | Chilocorus renipustulatus | Kidney-spot Ladybird | 17 | 2020 |
| beetle | Chlaenius nigricornis | a ground beetle | 2 | 2015 |
| beetle | Choleva agilis | a round fungus beetle | 14 | 2021 |
| beetle | Choleva fagniezi | a round fungus beetle | 1 | 1999 |
| beetle | Chrysolina | a Chrysolina species (unidentified) | 1 | 2009 |
| beetle | Chrysolina americana | Rosemary Beetle | 70 | 2022 |
| beetle | Chrysolina banksii | a leaf beetle | 2 | 2019 |
| beetle | Chrysolina fastuosa | Dead-nettle Leaf Beetle | 1 | 2021 |
| beetle | Chrysolina herbacea | Mint Leaf Beetle | 10 | 2021 |
| beetle | Chrysolina hyperici | a leaf beetle | 10 | 2019 |
| beetle | Chrysolina oricalcia | a leaf beetle | 13 | 2021 |
| beetle | Chrysolina polita | Knotgrass Leaf Beetle | 28 | 2021 |
| beetle | Chrysolina staphylaea | a leaf beetle | 31 | 2021 |
| beetle | Chrysolina sturmi | a leaf beetle | 3 | 2000 |
| beetle | Chrysolina varians | a leaf beetle | 3 | 2014 |
| beetle | Chrysomela | a Chrysomela species (unidentified) | 2 | 2013 |
| beetle | Chrysomela populi | Red Poplar Leaf Beetle | 2 | 2016 |
| beetle | Chrysomelidae | indet leaf beetle (unidentified) | 12 | 2018 |
| beetle | Cicindela campestris | Green Tiger Beetle | 22 | 2020 |
| beetle | Cilea silphoides | a rove beetle | 2 | 2014 |
| beetle | Cionus alauda | a weevil | 3 | 2021 |
| beetle | Cionus hortulanus | a weevil | 5 | 2022 |
| beetle | Cionus scrophulariae | Figwort Weevil | 52 | 2022 |
| beetle | Cionus tuberculosus | a weevil | 10 | 2020 |
| beetle | Cis bidentatus | a small fungus beetle | 1 | 2020 |
| beetle | Cis bilamellatus | a small fungus beetle | 28 | 2021 |
| beetle | Cis boleti | a small fungus beetle | 14 | 2021 |
| beetle | Cis fagi | a small fungus beetle | 7 | 2021 |
| beetle | Cis festivus | a small fungus beetle | 3 | 2020 |
| beetle | Cis micans | a small fungus beetle | 1 | 2021 |
| beetle | Cis nitidus | a small fungus beetle | 6 | 2016 |
| beetle | Clambus armadillo | an armadillo beetle | 1 | 1990 |
| beetle | Clitostethus arcuatus | a ladybird | 1 | 2018 |
| beetle | Clivina collaris | a ground beetle | 1 | 1967 |
| beetle | Clivina fossor | a ground beetle | 32 | 2021 |
| beetle | Clytra quadripunctata | a leaf beetle | 1 | 2003 |
| beetle | Clytus arietis | Wasp Beetle | 82 | 2020 |
| beetle | Coccidula rufa | a ladybird | 57 | 2019 |
| beetle | Coccidula scutellata | a ladybird | 6 | 2009 |
| beetle | Coccinella septempunctata | Seven-spot Ladybird | 1092 | 2022 |
| beetle | Coccinella undecimpunctata | 11-spot Ladybird | 20 | 2019 |
| beetle | Coccinellidae | a ladybird (unidentified) | 169 | 2021 |
| beetle | Coeliodes rana | a weevil | 7 | 2020 |
| beetle | Coelositona cambricus | a weevil | 1 | 2017 |
| beetle | Coelostoma orbiculare | a scavenger water beetle | 10 | 2011 |
| beetle | Coleoptera | a beetle (unidentified) | 115 | 2018 |
| beetle | Colymbetes fuscus | a water beetle | 76 | 2021 |
| beetle | Colymbetinae | a Colymbetinae species (unidentified) | 8 | 2013 |
| beetle | Conopalpus testaceus | a false darkling beetle | 1 | 2001 |
| beetle | Coprophilus striatulus | a rove beetle | 1 | 1982 |
| beetle | Cordalia obscura | a rove beetle | 1 | 2021 |
| beetle | Corticaria crenulata | a mould beetle | 4 | 2021 |
| beetle | Corticaria impressa | a mould beetle | 5 | 2020 |
| beetle | Corticaria umbilicata | a mould beetle | 1 | 2016 |
| beetle | Corticarina minuta | a mould beetle | 5 | 2020 |
| beetle | Cortinicara gibbosa | a mould beetle | 49 | 2021 |
| beetle | Creophilus maxillosus | Hairy Rove Beetle | 4 | 2019 |
| beetle | Crepidodera aurata | Willow Flea Beetle | 34 | 2021 |
| beetle | Crepidodera aurea | a leaf beetle | 27 | 2021 |
| beetle | Crepidodera fulvicornis | a leaf beetle | 10 | 2021 |
| beetle | Crepidodera plutus | an insect - beetle (Coleoptera) | 33 | 2021 |
| beetle | Crioceris asparagi | Asparagus Beetle | 2 | 2019 |
| beetle | Crudosilis ruficollis | a soldier beetle | 6 | 2021 |
| beetle | Cryptarcha strigata | a pollen or sap beetle | 6 | 2018 |
| beetle | Cryptocephalus | a Cryptocephalus species (unidentified) | 1 | 2009 |
| beetle | Cryptocephalus aureolus | a leaf beetle | 26 | 2021 |
| beetle | Cryptocephalus bipunctatus | a leaf beetle | 15 | 2017 |
| beetle | Cryptocephalus fulvus | a leaf beetle | 4 | 2019 |
| beetle | Cryptocephalus hypochaeridis | a leaf beetle | 2 | 2021 |
| beetle | Cryptocephalus labiatus | a leaf beetle | 10 | 2020 |
| beetle | Cryptocephalus moraei | a leaf beetle | 17 | 2020 |
| beetle | Cryptocephalus pusillus | a leaf beetle | 13 | 2021 |
| beetle | Cryptolaemus montrouzieri | a ladybird | 1 | 2014 |
| beetle | Cryptophagus dentatus | a silken fungus beetle | 9 | 2016 |
| beetle | Cryptophagus laticollis | a silken fungus beetle | 1 | 1999 |
| beetle | Cryptophagus pubescens | a silken fungus beetle | 1 | 2016 |
| beetle | Cryptophagus ruficornis | a silken fungus beetle | 1 | 2015 |
| beetle | Cryptophagus scanicus | a silken fungus beetle | 36 | 2021 |
| beetle | Cryptophagus setulosus | a silken fungus beetle | 1 | 1969 |
| beetle | Cryptopleurum minutum | a scavenger water beetle | 2 | 2021 |
| beetle | Cryptopleurum subtile | a scavenger water beetle | 1 | 1997 |
| beetle | Cryptorhynchus lapathi | Withy weevil | 1 | 2015 |
| beetle | Crypturgus cinereus | a weevil | 1 | 2015 |
| beetle | Ctenicera cuprea | a click beetle | 1 | 2019 |
| beetle | Cteniopus sulphureus | Sulphur Beetle | 31 | 2020 |
| beetle | Ctesias serra | Cobweb Beetle | 5 | 2015 |
| beetle | Curculio glandium | Acorn Weevil | 46 | 2022 |
| beetle | Curculionidae | a weevil (unidentified) | 24 | 2018 |
| beetle | Curculio nucum | Nut Weevil | 10 | 2019 |
| beetle | Curculio venosus | a weevil | 9 | 2021 |
| beetle | Curculio villosus | a weevil | 2 | 2020 |
| beetle | Curimopsis maritima | a pill beetle | 2 | 1938 |
| beetle | Curtonotus aulicus | a ground beetle | 11 | 2011 |
| beetle | Curtonotus convexiusculus | a ground beetle | 1 | 2019 |
| beetle | Cyanapion afer | a seed weevil | 11 | 2010 |
| beetle | Cychramus luteus | a pollen or sap beetle | 2 | 2015 |
| beetle | Cychrus caraboides | Snail Hunter | 20 | 2021 |
| beetle | Cymbiodyta marginellus | a scavenger water beetle | 43 | 2013 |
| beetle | Cypha longicornis | a rove beetle | 8 | 2021 |
| beetle | Cyphon coarctatus | a marsh beetle | 39 | 2021 |
| beetle | Cyphon laevipennis | a marsh beetle | 3 | 2009 |
| beetle | Cyphon ochraceus | a marsh beetle | 9 | 2018 |
| beetle | Cyphon padi | a marsh beetle | 2 | 2015 |
| beetle | Cyphon palustris | a marsh beetle | 1 | 2009 |
| beetle | Cyphon variabilis | a marsh beetle | 5 | 2015 |
| beetle | Cytilus sericeus | a pill beetle | 4 | 2016 |
| bird | Cairina moschata | Muscovy duck | 80 | 2018 |
| bird | Calcarius lapponicus | Lapland Bunting | 32 | 2021 |
| bird | Calidris | a Calidris species (unidentified) | 1 | 2019 |
| bird | Calidris alba | Sanderling | 1007 | 2021 |
| bird | Calidris alpina | Dunlin | 13779 | 2021 |
| bird | Calidris alpina arctica | Arctica Dunlin | 10 | 2021 |
| bird | Calidris alpina schinzii | schinzii Dunlin | 1 | 2018 |
| bird | Calidris bairdii | Baird's Sandpiper | 2 | 2001 |
| bird | Calidris canutus | Knot | 2616 | 2021 |
| bird | Calidris ferruginea | Curlew Sandpiper | 1797 | 2021 |
| bird | Calidris fuscicollis | White-rumped Sandpiper | 2 | 2001 |
| bird | Calidris maritima | Purple Sandpiper | 534 | 2021 |
| bird | Calidris melanotos | Pectoral Sandpiper | 117 | 2020 |
| bird | Calidris minuta | Little Stint | 1394 | 2021 |
| bird | Calidris pugnax | Ruff | 1987 | 2021 |
| bird | Calidris pusilla | Semipalmated Sandpiper | 1 | 2009 |
| bird | Calidris subruficollis | Buff-breasted Sandpiper | 1 | 1986 |
| bird | Calidris temminckii | Temminck's Stint | 54 | 2019 |
| bird | Calonectris diomedea | Cory's Shearwater | 1 | 2000 |
| bird | Caprimulgus europaeus | Nightjar | 61 | 2021 |
| bird | Carduelis | a Carduelis species (unidentified) | 3 | 2009 |
| bird | Carduelis carduelis | Goldfinch | 39772 | 2023 |
| bird | Carpodacus erythrinus | Common Rosefinch | 5 | 2017 |
| bird | Cecropis daurica | Red-rumped Swallow | 1 | 2012 |
| bird | Cepphus grylle | Black Guillemot | 4 | 2015 |
| bird | Certhia familiaris | Treecreeper | 5461 | 2022 |
| bird | Cettia cetti | Cetti's Warbler | 8713 | 2023 |
| bird | Charadriidae | a plover (unidentified) | 2 | 2016 |
| bird | Charadrius alexandrinus | Kentish Plover | 11 | 2018 |
| bird | Charadrius dubius | Little Ringed Plover | 3029 | 2022 |
| bird | Charadrius hiaticula | Ringed Plover | 7235 | 2021 |
| bird | Charadrius leschenaultii | Greater Sand Plover | 1 | 1986 |
| bird | Charadrius morinellus | Dotterel | 1 | 2014 |
| bird | Charadrius vociferus | Killdeer | 1 | 1986 |
| bird | Chlidonias hybrida | Whiskered Tern | 17 | 2016 |
| bird | Chlidonias leucopterus | White-winged Black Tern | 22 | 2014 |
| bird | Chlidonias niger | Black Tern | 1017 | 2021 |
| bird | Chlidonias niger surinamensis | American Black Tern | 3 | 1999 |
| bird | Chloris chloris | Greenfinch | 31252 | 2023 |
| bird | Chroicocephalus philadelphia | Bonaparte's Gull | 7 | 2017 |
| bird | Chroicocephalus ridibundus | Black-headed Gull | 22449 | 2023 |
| bird | Chrysolophus pictus | Golden Pheasant | 6 | 2019 |
| bird | Ciconia ciconia | White Stork | 50 | 2021 |
| bird | Cinclus cinclus | Dipper | 2732 | 2021 |
| bird | Circus | a harrier (unidentified) | 11 | 2021 |
| bird | Circus aeruginosus | Marsh Harrier | 2485 | 2021 |
| bird | Circus cyaneus | Hen Harrier | 263 | 2021 |
| bird | Circus macrourus | Pallid Harrier | 1 | 2016 |
| bird | Circus pygargus | Montagu's Harrier | 34 | 2015 |
| bird | Clangula hyemalis | Long-tailed Duck | 1156 | 2021 |
| bird | Coccothraustes coccothraustes | Hawfinch | 369 | 2021 |
| bird | Coloeus monedula | Jackdaw | 32383 | 2023 |
| bird | Coloeus monedula monedula | Nordic Jackdaw | 2 | 2019 |
| bird | Columba | a Columba species (unidentified) | 70 | 2022 |
| bird | Columba livia | Rock Dove | 1614 | 2021 |
| bird | Columba livia (feral pigeon) | Feral Pigeon | 26465 | 2022 |
| bird | Columba oenas | Stock Dove | 8491 | 2023 |
| bird | Columba palumbus | Woodpigeon | 63597 | 2023 |
| bird | Columba sp. or Streptopelia sp. (a pigeon or dove unidentified) | a pigeon or dove (unidentified) | 204 | 2021 |
| bird | Columbidae | a Columbidae species (unidentified) | 1 | 2021 |
| bird | Corvidae | a corvidae species (unidentified) | 97 | 2022 |
| bird | Corvus | a Corvus species (unidentified) | 122 | 2019 |
| bird | Corvus corax | Raven | 17099 | 2023 |
| bird | Corvus corone | Carrion Crow | 45847 | 2023 |
| bird | Corvus corone agg. | Carrion Crow/Hooded Crow | 1 | 2018 |
| bird | Corvus frugilegus | Rook | 16362 | 2022 |
| bird | Coturnix coturnix | Quail | 240 | 2021 |
| bird | Crex crex | Corncrake | 2 | 1986 |
| bird | Cuculus canorus | Cuckoo | 5402 | 2021 |
| bird | Curruca communis | Whitethroat | 10063 | 2022 |
| bird | Curruca curruca | Lesser Whitethroat | 4717 | 2022 |
| bird | Curruca undata | Dartford Warbler | 89 | 2020 |
| bird | Cyanistes caeruleus | Blue Tit | 64070 | 2023 |
| bird | Cygnus | a swan (unidentified) | 36 | 2022 |
| bird | Cygnus atratus | Black Swan | 166 | 2019 |
| bird | Cygnus columbianus | Bewick's Swan | 1104 | 2021 |
| bird | Cygnus cygnus | Whooper Swan | 194 | 2021 |
| bird | Cygnus melancoryphus | Black-necked Swan | 1 | 2008 |
| bird | Cygnus olor | Mute Swan | 18413 | 2022 |
| booklouse or barklouse | Cerobasis guestfalica | a booklouse or barklouse | 4 | 1995 |
| bryozoan | Conopeum reticulum | an encrusting bryozoan | 1 | 1997 |
| bryozoan | Cryptosula pallasiana | a bryozoan | 1 | 1937 |
| bug | Cacopsylla ambigua | a jumping plantlouse | 1 | 2009 |
| bug | Cacopsylla melanoneura | a jumping plantlouse | 4 | 2014 |
| bug | Cacopsylla peregrina | a jumping plantlouse | 2 | 2015 |
| bug | Cacopsylla pyricola | a jumping plantlouse | 1 | 2020 |
| bug | Callicorixa praeusta | a waterboatman | 19 | 2013 |
| bug | Calocoris | a Calocoris species (unidentified) | 1 | 2014 |
| bug | Calocoris (Calocoris) alpestris | a plantbug or grassbug | 7 | 2017 |
| bug | Calocoris (Calocoris) roseomaculatus | a plantbug or grassbug | 6 | 2012 |
| bug | Campyloneura virgula | a plantbug or grassbug | 35 | 2022 |
| bug | Campylosteira verna | a lace bug | 1 | 2018 |
| bug | Capsodes gothicus | a plantbug or grassbug | 1 | 1987 |
| bug | Capsus ater | a plantbug or grassbug | 94 | 2021 |
| bug | Cardiastethus fasciiventris | a flower bug or bloodsucking bug | 5 | 2021 |
| bug | Cavariella (Cavariella) aegopodii | Willow-Carrot Aphid | 22 | 1985 |
| bug | Centrotus cornutus | Tree Hopper | 40 | 2021 |
| bug | Ceraleptus lividus | a squashbug | 1 | 2019 |
| bug | Cercopidae | a froghopper (unidentified) | 12 | 2021 |
| bug | Cercopis vulnerata | Red-and-black Froghopper | 148 | 2022 |
| bug | Chaetosiphon (Pentatrichopus) fragaefolii | Strawberry Aphid | 5 | 1975 |
| bug | Charagochilus (Charagochilus) gyllenhalii | a plantbug or grassbug | 1 | 1990 |
| bug | Chartoscirta cincta | a shore bug | 9 | 2016 |
| bug | Chartoscirta cocksii | a shore bug | 7 | 2015 |
| bug | Chilacis typhae | a ground bug | 5 | 2021 |
| bug | Chloriona dorsata | a planthopper | 4 | 2009 |
| bug | Chloriona glaucescens | a planthopper | 5 | 2019 |
| bug | Chloriona unicolor | a planthopper | 5 | 2009 |
| bug | Cicadella viridis | a leafhopper | 66 | 2021 |
| bug | Cicadellidae | a Cicadellidae species (unidentified) | 11 | 2019 |
| bug | Cicadula persimilis | a leafhopper | 6 | 2009 |
| bug | Cicadula quadrinotata | a leafhopper | 3 | 2009 |
| bug | Cimex lectularius | Bedbug | 1 | 1900 |
| bug | Cimex pipistrelli | Batbug | 3 | 2018 |
| bug | Cinara sp. | a hairy conifer aphid (unidentified) | 8 | 1975 |
| bug | Cixius distinguendus | a lacehopper | 2 | 2001 |
| bug | Cixius nervosus | a lacehopper | 18 | 2021 |
| bug | Cixius remotus | a lacehopper | 1 | 2001 |
| bug | Closterotomus fulvomaculatus | a plantbug or grassbug | 4 | 2011 |
| bug | Closterotomus norwegicus | Potato Capsid | 103 | 2022 |
| bug | Closterotomus trivialis | a plantbug or grassbug | 2 | 2022 |
| bug | Coccoidea sp. | a scale insect (unidentified) | 1 | 2012 |
| bug | Coccus hesperidum | Brown Soft-scale | 4 | 2017 |
| bug | Compsidolon (Coniortodes) salicellum | a plantbug or grassbug | 4 | 2020 |
| bug | Conomelus anceps | a planthopper | 20 | 2021 |
| bug | Conosanus obsoletus | a leafhopper | 3 | 2020 |
| bug | Coranus (Coranus) subapterus | an assassin bug | 1 | 1957 |
| bug | Coreidae | a Coreidae species (unidentified) | 1 | 2014 |
| bug | Coreus marginatus | Dock Bug | 320 | 2021 |
| bug | Coriomeris denticulatus | a squashbug | 34 | 2021 |
| bug | Corixa | a Corixa waterboatman (unidentified) | 91 | 2018 |
| bug | Corixa affinis | a waterboatman | 1 | 1992 |
| bug | Corixa dentipes | a waterboatman | 1 | 2013 |
| bug | Corixa panzeri | a waterboatman | 4 | 2012 |
| bug | Corixa punctata | Punctate Corixa | 98 | 2018 |
| bug | Corixidae | a Corixidae water-boatman (unidentified) | 59 | 2021 |
| bug | Corixidae sp. or Notonectidae sp. or Pleidae sp. (unidentified) | a waterboatman or water-boatman or backswimmer (unidentified) | 39 | 2018 |
| bug | Corizus hyoscyami | a bug | 94 | 2022 |
| bug | Cryptomyzus (Cryptomyzus) ribis | an aphid | 1 | 2019 |
| bug | Cyllecoris histrionius | a plantbug or grassbug | 29 | 2020 |
| bug | Cymatia coleoptrata | a waterboatman | 3 | 2004 |
| bug | Cymus claviculus | a stiltbug | 1 | 2009 |
| bug | Cymus glandicolor | a stiltbug | 24 | 2020 |
| bug | Cymus melanocephalus | a stiltbug | 17 | 2021 |
| bug | Cyphostethus tristriatus | Juniper Shieldbug | 26 | 2022 |
| caddis fly | Ceraclea | a Ceraclea caddisfly (unidentified) | 1 | 2018 |
| caddis fly | Ceraclea dissimilis | a caddisfly | 2 | 2014 |
| caddis fly | Ceraclea fulva | a caddisfly | 1 | 1995 |
| caddis fly | Ceraclea senilis | a caddisfly | 1 | 2012 |
| caddis fly | Chaetopteryx villosa | a caddisfly | 12 | 2019 |
| caddis fly | Crunoecia irrorata | a caddisfly | 1 | 2001 |
| caddis fly | Cyrnus | a Cyrnus species (unidentified) | 1 | 1991 |
| caddis fly | Cyrnus trimaculatus | a caddisfly | 1 | 2013 |
| centipede | Chilopoda | a Centipede (unidentified) | 32 | 2016 |
| centipede | Cryptops | a Cryptops species (unidentified) | 1 | 2019 |
| centipede | Cryptops hortensis | Common cryptops | 10 | 2011 |
| centipede | Cryptops parisi | Paris cryptops | 6 | 2013 |
| crustacean | Calliopius laeviusculus | a crustacean | 1 | 1939 |
| crustacean | Cancer pagurus | Edible Crab | 2 | 2003 |
| crustacean | Carcinus maenas | Green Shore Crab | 22 | 2019 |
| crustacean | Chelura terebrans | a crustacean | 1 | 1939 |
| crustacean | Chirocephalus diaphanus | Fairy Shrimp | 2 | 2013 |
| crustacean | Corophium volutator | a crustacean | 3 | 1939 |
| crustacean | Crangon crangon | Brown Shrimp | 10 | 2016 |
| crustacean | Crangonyx pseudogracilis/floridanus (sens. lat.) | Northern River Crangonyctid | 254 | 2016 |
| crustacean | Cumopsis goodsir | a crustacean | 1 | 1976 |
| crustacean | Cyclopoida | a Cyclopoida species (unidentified) | 2 | 2010 |
| crustacean | Cyclops | a Cyclops species (unidentified) | 8 | 2012 |
| crustacean | Cypris | a Cypris species (unidentified) | 1 | 2010 |
| diatom | Caloneis fasciata | a diatom | 2 | 2016 |
| diatom | Centric diatoms | a diatom | 1 | 2015 |
| diatom | Cocconeis placentula | a diatom | 1 | 2015 |
| diatom | Cocconeis placentula var. euglypta | a diatom | 2 | 2015 |
| diatom | Cocconeis placentula var. lineata | a diatom | 1 | 2015 |
| diatom | Cyclotella | a Cyclotella diatom species (unidentified) | 1 | 2003 |
| dragonfly, hawker or damselfly | Calopteryx | a Calopteryx species (unidentified) | 12 | 2018 |
| dragonfly, hawker or damselfly | Calopteryx splendens | Banded Demoiselle | 1544 | 2022 |
| dragonfly, hawker or damselfly | Calopteryx virgo | Beautiful Demoiselle | 1119 | 2022 |
| dragonfly, hawker or damselfly | Coenagrion | a Coenagrion species (unidentified) | 15 | 2012 |
| dragonfly, hawker or damselfly | Coenagrionidae | a Coenagrionidae damselfly (unidentified) | 57 | 2018 |
| dragonfly, hawker or damselfly | Coenagrion puella | Azure Damselfly | 3385 | 2022 |
| dragonfly, hawker or damselfly | Coenagrion pulchellum | Variable Damselfly | 139 | 2019 |
| dragonfly, hawker or damselfly | Cordulegaster boltonii | Golden-ringed Dragonfly | 31 | 2021 |
| dragonfly, hawker or damselfly | Cordulia aenea | Downy Emerald | 7 | 1989 |
| false scorpion | Chernes cimicoides | a false scorpion | 1 | 2001 |
| false scorpion | Chthonius | a false scorpion (unidentified) | 1 | 2019 |
| false scorpion | Chthonius (Chthonius) | a false scorpion (Pseudoscorpiones) | 1 | 2009 |
| false scorpion | Chthonius ischnocheles | a false scorpion | 2 | 1999 |
| false scorpion | Chthonius orthodactylus (sens.str.) | a false scorpion | 1 | 2013 |
| fish | Callionymus lyra | Dragonet | 3 | 1940 |
| fish | Capros aper | Boarfish | 1 | 1940 |
| fish | Carassius auratus | Goldfish | 21 | 2018 |
| fish | Carassius carassius | Crucian Carp | 2 | 1995 |
| fish | Centrolabrus exoletus | Rock Cook | 1 | 1938 |
| fish | Chelidonichthys cuculus | Red Gurnard | 3 | 1940 |
| fish | Chelidonichthys lastoviza | Streaked Gurnard | 1 | 1879 |
| fish | Chelidonichthys lucerna | Tub Gurnard | 2 | 1994 |
| fish | Chelon labrosus | Thick-lipped Mullet | 5 | 2018 |
| fish | Ciliata mustela | Five-bearded Rockling | 3 | 2009 |
| fish | Clupea harengus | Herring | 4 | 1940 |
| fish | Conger conger | Conger Eel | 7 | 2021 |
| fish | Cottidae | a Cottidae species (unidentified) | 1 | 2000 |
| fish | Cottus gobio | Bullhead | 228 | 2022 |
| fish | Cyclopterus lumpus | Lumpsucker | 5 | 1980 |
| fish | Cyprinus | a Cyprinus species (unidentified) | 1 | 1988 |
| fish | Cyprinus carpio | Carp | 23 | 2019 |
| flea | Ceratophyllus (Ceratophyllus) gallinae | hen flea | 1 | 1976 |
| flea | Ctenocephalides felis subsp. felis | cat flea | 1 | 2002 |
| fungus | Calcarisporium arbuscula | a fungus | 1 | 2014 |
| fungus | Calloria neglecta | an ascomycete fungus | 18 | 2013 |
| fungus | Calocera cornea | a basidiomycete fungus | 47 | 2018 |
| fungus | Calocera pallidospathulata | a basidiomycete fungus | 4 | 2012 |
| fungus | Calocera viscosa | a basidiomycete fungus | 63 | 2017 |
| fungus | Calocybe carnea | a basidiomycete fungus | 76 | 2014 |
| fungus | Calocybe gambosa | St. George's Mushroom | 130 | 2015 |
| fungus | Calocybe ionides | a basidiomycete fungus | 5 | 2005 |
| fungus | Calvatia gigantea | Giant Puffball | 34 | 2020 |
| fungus | Calycina herbarum | an ascomycete fungus | 5 | 2010 |
| fungus | Calyptella campanula | a basidiomycete fungus | 3 | 2008 |
| fungus | Calyptella capula | a basidiomycete fungus | 12 | 2013 |
| fungus | Camarophyllopsis atropuncta | a basidiomycete fungus | 2 | 2010 |
| fungus | Camarophyllopsis foetens | a basidiomycete fungus | 2 | 2010 |
| fungus | Camarosporium tiliae | a fungus | 1 | 2013 |
| fungus | Candelabrum spinulosum | a fungus | 1 | 2012 |
| fungus | Cantharellus cibarius | Chanterelle | 4 | 2012 |
| fungus | Cantharellus tubaeformis | a chantarelle | 3 | 2012 |
| fungus | Cercidospora epipolytropa | a fungus | 2 | 2004 |
| fungus | Cercospora depazeoides | a fungus | 2 | 2015 |
| fungus | Cercospora scandens | a fungus | 1 | 2014 |
| fungus | Ceriporia purpurea | a basidiomycete fungus | 1 | 2012 |
| fungus | Ceriporia reticulata | a basidiomycete fungus | 8 | 2013 |
| fungus | Ceriporia viridans | a basidiomycete fungus | 5 | 2014 |
| fungus | Ceriporiopsis pannocincta | a fungus | 1 | 2008 |
| fungus | Cerrena unicolor | a basidiomycete fungus | 3 | 2013 |
| fungus | Chaetosphaerella phaeostroma | an ascomycete fungus | 52 | 2020 |
| fungus | Chalciporus piperatus | Peppery Bolete | 9 | 2019 |
| fungus | Chamaemyces fracidus | an agaric | 3 | 2008 |
| fungus | Cheilymenia fimicola | a fungus | 3 | 2014 |
| fungus | Cheilymenia granulata | a fungus | 11 | 2014 |
| fungus | Cheilymenia stercorea | a fungus | 2 | 1999 |
| fungus | Chlorociboria aeruginascens | an ascomycete fungus | 46 | 2020 |
| fungus | Chlorociboria aeruginosa | an ascomycete fungus | 1 | 2008 |
| fungus | Chlorophyllum brunneum | an agaric | 5 | 2011 |
| fungus | Chlorophyllum olivieri | a fungus | 12 | 2013 |
| fungus | Chlorophyllum rachodes | Shaggy Parasol | 82 | 2020 |
| fungus | Chondrostereum purpureum | Silverleaf Fungus | 52 | 2022 |
| fungus | Chromocyphella muscicola | an agaric | 1 | 2013 |
| fungus | Chroogomphus rutilus | Pine Spike-cap | 56 | 2019 |
| fungus | Chrysomphalina grossula | a basidiomycete fungus | 2 | 2014 |
| fungus | Ciboria batschiana | an ascomycete fungus | 1 | 1970 |
| fungus | Clathrus archeri | Devil's Fingers | 3 | 2019 |
| fungus | Clavaria acuta | a chantarelle | 16 | 2014 |
| fungus | Clavaria asperulispora | a fungus | 2 | 2008 |
| fungus | Clavaria falcata | a fungus | 3 | 2008 |
| fungus | Clavaria fragilis | a chantarelle | 23 | 2019 |
| fungus | Clavaria fumosa | a chantarelle | 16 | 2013 |
| fungus | Claviceps purpurea | an ergot fungus | 13 | 2017 |
| fungus | Claviceps purpurea var. purpurea | Ergot | 14 | 2017 |
| fungus | Claviceps purpurea var. spartinae | an ergot fungus | 6 | 2021 |
| fungus | Clavulina cinerea | a chantarelle | 51 | 2020 |
| fungus | Clavulina coralloides | a chantarelle | 45 | 2020 |
| fungus | Clavulina rugosa | a chantarelle | 35 | 2014 |
| fungus | Clavulinopsis corniculata | a chantarelle | 62 | 2020 |
| fungus | Clavulinopsis fusiformis | a chantarelle | 6 | 2017 |
| fungus | Clavulinopsis helvola | a chantarelle | 47 | 2020 |
| fungus | Clavulinopsis laeticolor | a chantarelle | 11 | 2013 |
| fungus | Clavulinopsis luteoalba | a chantarelle | 12 | 2019 |
| fungus | Clitocybe | a Clitocybe basidiomycete fungus (unidentified) | 8 | 2005 |
| fungus | Clitocybe agrestis | a fungus | 18 | 2013 |
| fungus | Clitocybe amarescens | a fungus | 5 | 2014 |
| fungus | Clitocybe americana | a fungus | 1 | 2007 |
| fungus | Clitocybe angustissima | a basidiomycete fungus | 2 | 2006 |
| fungus | Clitocybe brumalis | a basidiomycete fungus | 2 | 1985 |
| fungus | Clitocybe candicans | a basidiomycete fungus | 2 | 2002 |
| fungus | Clitocybe costata | a basidiomycete fungus | 17 | 2010 |
| fungus | Clitocybe dealbata | Ivory Funnel | 9 | 2014 |
| fungus | Clitocybe diatreta | a basidiomycete fungus | 4 | 2012 |
| fungus | Clitocybe ditopa | a basidiomycete fungus | 11 | 2014 |
| fungus | Clitocybe ericetorum | a basidiomycete fungus | 2 | 1986 |
| fungus | Clitocybe fragrans | a basidiomycete fungus | 140 | 2020 |
| fungus | Clitocybe geotropa | a basidiomycete fungus | 56 | 2022 |
| fungus | Clitocybe gibba | Common Funnel | 74 | 2014 |
| fungus | Clitocybe harmajae | a basidiomycete fungus | 1 | 1996 |
| fungus | Clitocybe houghtonii | a basidiomycete fungus | 2 | 1987 |
| fungus | Clitocybe hydrogramma | a basidiomycete fungus | 19 | 2005 |
| fungus | Clitocybe infundibuliformis | Common Funnel Cap | 17 | 2009 |
| fungus | Clitocybe marginella | a fungus | 2 | 2010 |
| fungus | Clitocybe metachroa | a basidiomycete fungus | 88 | 2014 |
| fungus | Clitocybe nebularis | Clouded Agaric | 298 | 2020 |
| fungus | Clitocybe obsoleta | a basidiomycete fungus | 7 | 2003 |
| fungus | Clitocybe odora | Aniseed Toadstool | 27 | 2014 |
| fungus | Clitocybe phaeophthalma | a basidiomycete fungus | 66 | 2015 |
| fungus | Clitocybe phyllophila | Frosty Funnel | 54 | 2019 |
| fungus | Clitocybe rivulosa | a basidiomycete fungus | 159 | 2015 |
| fungus | Clitocybe sinopica | a basidiomycete fungus | 15 | 2006 |
| fungus | Clitocybe subspadicea | a fungus | 2 | 2003 |
| fungus | Clitocybe truncicola | a basidiomycete fungus | 1 | 2014 |
| fungus | Clitocybe umbilicata | a basidiomycete fungus | 1 | 1995 |
| fungus | Clitocybe vibecina | a basidiomycete fungus | 22 | 2020 |
| fungus | Clitopilus hobsonii | a basidiomycete fungus | 5 | 2013 |
| fungus | Clitopilus prunulus | Miller (The) [fungus] | 190 | 2022 |
| fungus | Cochliobolus verruculosus | a fungus | 1 | 2014 |
| fungus | Coleosporium tussilaginis | a rust | 9 | 2017 |
| fungus | Coleroa robertiani | a fungus | 2 | 2017 |
| fungus | Collybia cirrhata | a basidiomycete fungus | 3 | 2011 |
| fungus | Collybia cookei | a basidiomycete fungus | 6 | 2012 |
| fungus | Coniophora puteana | Cellar Fungus | 27 | 2015 |
| fungus | Conocybe | a Conocybe species (unidentified) | 3 | 2005 |
| fungus | Conocybe alboradicans | an agaric | 1 | 1992 |
| fungus | Conocybe ambigua | an agaric | 8 | 2008 |
| fungus | Conocybe anthracophila | an agaric | 1 | 2002 |
| fungus | Conocybe apala | an agaric | 42 | 2014 |
| fungus | Conocybe aporos | an agaric | 61 | 2014 |
| fungus | Conocybe arrhenii | an agaric | 36 | 2014 |
| fungus | Conocybe bisporigera | an agaric | 3 | 2010 |
| fungus | Conocybe blattaria | an agaric | 3 | 2013 |
| fungus | Conocybe brachypodii | a fungus | 16 | 2014 |
| fungus | Conocybe brunnea | an agaric | 13 | 2009 |
| fungus | Conocybe dentatomarginata (nom. nud.) | an agaric | 14 | 2009 |
| fungus | Conocybe echinata | an agaric | 18 | 2009 |
| fungus | Conocybe enderlei | an agaric | 1 | 2006 |
| fungus | Conocybe exannulata | an agaric | 1 | 2008 |
| fungus | Conocybe farinacea | an agaric | 2 | 2010 |
| fungus | Conocybe fragilis | an agaric | 1 | 1999 |
| fungus | Conocybe fuscimarginata | an agaric | 4 | 1991 |
| fungus | Conocybe hadrocystis | an agaric | 2 | 2008 |
| fungus | Conocybe incarnata | a fungus | 1 | 1999 |
| fungus | Conocybe juniana | an agaric | 2 | 2014 |
| fungus | Conocybe juniana var. juniana | an agaric | 19 | 2011 |
| fungus | Conocybe lenticulospora | an agaric | 3 | 2008 |
| fungus | Conocybe leucopus | an agaric | 4 | 1988 |
| fungus | Conocybe macrocephala | an agaric | 20 | 2013 |
| fungus | Conocybe macrospora | an agaric | 10 | 2014 |
| fungus | Conocybe mairei | an agaric | 3 | 2004 |
| fungus | Conocybe mesospora | an agaric | 34 | 2013 |
| fungus | Conocybe moseri | an agaric | 3 | 2005 |
| fungus | Conocybe pilosella | an agaric | 14 | 2010 |
| fungus | Conocybe plicatella | an agaric | 25 | 2010 |
| fungus | Conocybe pubescens | an agaric | 15 | 2012 |
| fungus | Conocybe pulchella | an agaric | 23 | 2011 |
| fungus | Conocybe pygmaeoaffinis | an agaric | 2 | 1992 |
| fungus | Conocybe rickeniana | an agaric | 13 | 2014 |
| fungus | Conocybe rickenii | an agaric | 49 | 2014 |
| fungus | Conocybe rostellata | a fungus | 5 | 2013 |
| fungus | Conocybe rugosa | an agaric | 11 | 2014 |
| fungus | Conocybe semiglobata | an agaric | 26 | 2014 |
| fungus | Conocybe siennophylla | an agaric | 45 | 2012 |
| fungus | Conocybe siliginea | an agaric | 15 | 2014 |
| fungus | Conocybe subovalis | an agaric | 15 | 2010 |
| fungus | Conocybe subpallida | a fungus | 6 | 2009 |
| fungus | Conocybe subpubescens | an agaric | 5 | 2010 |
| fungus | Conocybe tenera | Brown Cone-cap | 11 | 2014 |
| fungus | Conocybe utriformis | an agaric | 2 | 2014 |
| fungus | Conocybe velata | an agaric | 19 | 2014 |
| fungus | Conocybe velutipes | an agaric | 15 | 2010 |
| fungus | Conocybe vestita | an agaric | 8 | 2013 |
| fungus | Conocybe vexans | an agaric | 1 | 1990 |
| fungus | Coprinellus angulatus | an agaric | 1 | 2008 |
| fungus | Coprinellus callinus | an agaric | 8 | 2013 |
| fungus | Coprinellus canistri | an agaric | 1 | 2007 |
| fungus | Coprinellus disseminatus | Fairy Inkcap | 93 | 2020 |
| fungus | Coprinellus domesticus | an agaric | 46 | 2014 |
| fungus | Coprinellus ellisii | an agaric | 8 | 2009 |
| fungus | Coprinellus ephemerus | an agaric | 7 | 2002 |
| fungus | Coprinellus flocculosus | an agaric | 6 | 2008 |
| fungus | Coprinellus heptemerus | an agaric | 1 | 1996 |
| fungus | Coprinellus heterosetulosus | an agaric | 2 | 2009 |
| fungus | Coprinellus heterothrix | a fungus | 2 | 2009 |
| fungus | Coprinellus hiascens | an agaric | 2 | 1998 |
| fungus | Coprinellus impatiens | an agaric | 20 | 2017 |
| fungus | Coprinellus micaceus | Glistening Ink-cap | 285 | 2022 |
| fungus | Coprinellus pellucidus | an agaric | 2 | 1998 |
| fungus | Coprinellus plagioporus | an agaric | 1 | 2014 |
| fungus | Coprinellus radians | an agaric | 2 | 2013 |
| fungus | Coprinellus silvaticus | an agaric | 9 | 2000 |
| fungus | Coprinellus subimpatiens | an agaric | 3 | 2012 |
| fungus | Coprinellus xanthothrix | an agaric | 16 | 2020 |
| fungus | Coprinopsis | a Coprinopsis species (unidentified) | 3 | 2008 |
| fungus | Coprinopsis acuminata | an agaric | 2 | 2003 |
| fungus | Coprinopsis atramentaria | Common Ink-cap | 62 | 2021 |
| fungus | Coprinopsis candidata | an agaric | 1 | 2014 |
| fungus | Coprinopsis cinerea | an agaric | 4 | 2009 |
| fungus | Coprinopsis cordispora | an agaric | 2 | 2007 |
| fungus | Coprinopsis cothurnata | an agaric | 3 | 2014 |
| fungus | Coprinopsis echinospora | an agaric | 4 | 2000 |
| fungus | Coprinopsis friesii | an agaric | 2 | 1989 |
| fungus | Coprinopsis herinkii | a fungus | 1 | 2002 |
| fungus | Coprinopsis jonesii | a fungus | 1 | 2008 |
| fungus | Coprinopsis lagopus | Hare'sfoot Inkcap | 1 | 2021 |
| fungus | Coprinopsis lagopus var. lagopus | Haresfoot Inkcap | 81 | 2018 |
| fungus | Coprinopsis lagopus var. vacillans | an agaric | 2 | 2009 |
| fungus | Coprinopsis marcescibilis | an agaric | 12 | 2012 |
| fungus | Coprinopsis narcotica | an agaric | 2 | 1985 |
| fungus | Coprinopsis nivea | an agaric | 33 | 2013 |
| fungus | Coprinopsis pannucioides | an agaric | 2 | 1990 |
| fungus | Coprinopsis phaeospora | a fungus | 2 | 2010 |
| fungus | Coprinopsis picacea | Magpie Fungus | 4 | 2018 |
| fungus | Coprinopsis pseudofriesii | a fungus | 1 | 2013 |
| fungus | Coprinopsis pseudonivea | a fungus | 4 | 2009 |
| fungus | Coprinopsis radiata | an agaric | 1 | 2009 |
| fungus | Coprinopsis spelaiophila | a fungus | 9 | 2014 |
| fungus | Coprinopsis urticicola | an agaric | 2 | 2010 |
| fungus | Coprinus | an ink-cap (unidentified) | 6 | 2017 |
| fungus | Coprinus comatus | Shaggy Ink-cap | 87 | 2020 |
| fungus | Coprinus cortinatus | an agaric | 17 | 2012 |
| fungus | Coprinus ephemeroides | an agaric | 1 | 2004 |
| fungus | Coprinus eurysporus | an agaric | 1 | 2004 |
| fungus | Coprinus patouillardii | an agaric | 1 | 2001 |
| fungus | Cordyceps militaris | Scarlet Caterpillar Fungus | 12 | 2022 |
| fungus | Coriolaceae | a Coriolaceae species (unidentified) | 1 | 2012 |
| fungus | Corticium | a Corticium species (unidentified) | 1 | 1970 |
| fungus | Cortinarius | a Cortinarius agaric (unidentified) | 13 | 2019 |
| fungus | Cortinarius acutus | an agaric | 2 | 2006 |
| fungus | Cortinarius alboviolaceus | an agaric | 4 | 2010 |
| fungus | Cortinarius aleuriosmus | an agaric | 1 | 1998 |
| fungus | Cortinarius amoenolens | an agaric | 12 | 2004 |
| fungus | Cortinarius anomalus | an agaric | 84 | 2014 |
| fungus | Cortinarius anthracinus | an agaric | 1 | 2008 |
| fungus | Cortinarius armillatus | an agaric | 1 | 2004 |
| fungus | Cortinarius balaustinus | an agaric | 5 | 2010 |
| fungus | Cortinarius bibulus | an agaric | 1 | 2005 |
| fungus | Cortinarius bivelus | an agaric | 2 | 2010 |
| fungus | Cortinarius brunneofulvus | an agaric | 1 | 1987 |
| fungus | Cortinarius brunneus var. glandicolor | an agaric | 1 | 1987 |
| fungus | Cortinarius caerulescens | an agaric | 6 | 1998 |
| fungus | Cortinarius callochrous var. callochrous | an agaric | 10 | 2014 |
| fungus | Cortinarius callochrous var. parvus | an agaric | 2 | 2000 |
| fungus | Cortinarius casimirii | an agaric | 3 | 2010 |
| fungus | Cortinarius cinnamomeus | Cinnamon Webcap | 5 | 2013 |
| fungus | Cortinarius cisticola | an agaric | 4 | 2012 |
| fungus | Cortinarius croceocoeruleus | an agaric | 1 | 2014 |
| fungus | Cortinarius croceus | an agaric | 3 | 2013 |
| fungus | Cortinarius cyanopus | an agaric | 2 | 1990 |
| fungus | Cortinarius decipiens | an agaric | 10 | 2013 |
| fungus | Cortinarius decipiens var. decipiens | an agaric | 3 | 2008 |
| fungus | Cortinarius delibutus | an agaric | 1 | 1996 |
| fungus | Cortinarius dibaphus | an agaric | 1 | 1994 |
| fungus | Cortinarius elegantissimus | an agaric | 1 | 2008 |
| fungus | Cortinarius evernius | an agaric | 3 | 1996 |
| fungus | Cortinarius flexipes | an agaric | 2 | 2013 |
| fungus | Cortinarius flexipes var. flexipes | an agaric | 1 | 2005 |
| fungus | Cortinarius glaucopus | an agaric | 6 | 2011 |
| fungus | Cortinarius helobius | an agaric | 5 | 2010 |
| fungus | Cortinarius helvelloides | an agaric | 6 | 2009 |
| fungus | Cortinarius hemitrichus | an agaric | 5 | 2012 |
| fungus | Cortinarius hinnuleus | an agaric | 2 | 2001 |
| fungus | Cortinarius imbutus | an agaric | 2 | 2010 |
| fungus | Cortinarius infractus | an agaric | 16 | 2010 |
| fungus | Cortinarius largus | an agaric | 2 | 2007 |
| fungus | Cortinarius livido-ochraceus | an agaric | 1 | 2005 |
| fungus | Cortinarius malachius | an agaric | 2 | 1987 |
| fungus | Cortinarius obtusus | an agaric | 2 | 1990 |
| fungus | Cortinarius ochroleucus | an agaric | 3 | 2005 |
| fungus | Cortinarius olearioides | an agaric | 5 | 2010 |
| fungus | Cortinarius olidus | an agaric | 1 | 1998 |
| fungus | Cortinarius olivaceofuscus | an agaric | 4 | 2010 |
| fungus | Cortinarius osmophorus | an agaric | 1 | 1999 |
| fungus | Cortinarius paleaceus | an agaric | 5 | 1998 |
| fungus | Cortinarius privignoides | an agaric | 1 | 2009 |
| fungus | Cortinarius psammocephalus | an agaric | 1 | 2005 |
| fungus | Cortinarius purpurascens | an agaric | 6 | 2014 |
| fungus | Cortinarius rigens | an agaric | 1 | 2005 |
| fungus | Cortinarius rigidus | an agaric | 2 | 2005 |
| fungus | Cortinarius roseipes | an agaric | 2 | 2011 |
| fungus | Cortinarius rufo-olivaceus | an agaric | 1 | 1999 |
| fungus | Cortinarius sanguineus | an agaric | 3 | 2012 |
| fungus | Cortinarius saporatus | an agaric | 1 | 1996 |
| fungus | Cortinarius saturninus | an agaric | 9 | 2010 |
| fungus | Cortinarius semisanguineus | an agaric | 1 | 2012 |
| fungus | Cortinarius simulatus | an agaric | 1 | 2007 |
| fungus | Cortinarius sodagnitus | an agaric | 2 | 2007 |
| fungus | Cortinarius stillatitius | an agaric | 1 | 2000 |
| fungus | Cortinarius subbalaustinus | an agaric | 6 | 2010 |
| fungus | Cortinarius tabularis | an agaric | 1 | 1970 |
| fungus | Cortinarius torvus | an agaric | 1 | 2000 |
| fungus | Cortinarius triumphans | an agaric | 2 | 1994 |
| fungus | Cortinarius trivialis | an agaric | 1 | 1999 |
| fungus | Cortinarius umbrinolens | an agaric | 12 | 2013 |
| fungus | Cortinarius variicolor | an agaric | 2 | 1996 |
| fungus | Cortinarius venetus | an agaric | 1 | 2005 |
| fungus | Cortinarius violaceus | an agaric | 1 | 2021 |
| fungus | Craterellus cornucopioides | Horn of Plenty | 3 | 2000 |
| fungus | Crepidotus applanatus | an agaric | 7 | 2022 |
| fungus | Crepidotus applanatus var. applanatus | an agaric | 11 | 2013 |
| fungus | Crepidotus autochthonus | an agaric | 6 | 2008 |
| fungus | Crepidotus caspari | an agaric | 17 | 2014 |
| fungus | Crepidotus cesatii | an agaric | 79 | 2020 |
| fungus | Crepidotus cesatii var. subsphaerosporus | an agaric | 22 | 2002 |
| fungus | Crepidotus epibryus | an agaric | 16 | 2020 |
| fungus | Crepidotus luteolus | an agaric | 11 | 2020 |
| fungus | Crepidotus mollis | Soft Slipper Toadstool | 74 | 2020 |
| fungus | Crepidotus variabilis | Variable Oysterling | 69 | 2020 |
| fungus | Crepidotus versutus | an agaric | 4 | 2009 |
| fungus | Crinipellis scabella | a basidiomycete fungus | 26 | 2020 |
| fungus | Cristulariella depraedans | a fungus | 9 | 2014 |
| fungus | Crocicreas cyathoideum var. cyathoideum | an ascomycete fungus | 6 | 1999 |
| fungus | Crucibulum laeve | White-egg Bird's Nest | 6 | 2019 |
| fungus | Cryptosphaeria eunomia | an ascomycete fungus | 1 | 2010 |
| fungus | Cryptostroma corticale | a fungus | 1 | 1987 |
| fungus | Cryptovalsa protracta | an ascomycete fungus | 2 | 1999 |
| fungus | Cudoniella acicularis | an ascomycete fungus | 2 | 2008 |
| fungus | Cumminsiella mirabilissima | a rust | 3 | 2020 |
| fungus | Cyathus olla | Field Bird's Nest | 10 | 2019 |
| fungus | Cyathus striatus | Fluted Bird's Nest | 21 | 2019 |
| fungus | Cylindrobasidium | a Cylindrobasidium species (unidentified) | 1 | 2012 |
| fungus | Cylindrobasidium laeve | a basidiomycete fungus | 13 | 2013 |
| fungus | Cymadothea trifolii | a fungus | 2 | 2010 |
| fungus | Cystoderma amianthinum | an agaric | 75 | 2015 |
| fungus | Cystoderma simulatum | an agaric | 1 | 2015 |
| fungus | Cystodermella granulosa | an agaric | 1 | 2005 |
| fungus | Cystolepiota adulterina | an agaric | 10 | 2003 |
| fungus | Cystolepiota bucknallii | an agaric | 17 | 2007 |
| fungus | Cystolepiota fumosifolia | an agaric | 1 | 2013 |
| fungus | Cystolepiota hetieri | an agaric | 13 | 2008 |
| fungus | Cystolepiota moelleri | an agaric | 4 | 2008 |
| fungus | Cystolepiota seminuda | an agaric | 51 | 2014 |
| fungus | Cystolepiota sistrata | an agaric | 29 | 2001 |
| grasshopper, cricket or true cricket | Chorthippus | a Chorthippus species (unidentified) | 6 | 2008 |
| grasshopper, cricket or true cricket | Chorthippus albomarginatus | Lesser Marsh Grasshopper | 72 | 2021 |
| grasshopper, cricket or true cricket | Chorthippus brunneus | Common Field Grasshopper | 603 | 2022 |
| grasshopper, cricket or true cricket | Chorthippus parallelus | Meadow Grasshopper | 951 | 2021 |
| grasshopper, cricket or true cricket | Conocephalus | a Conocephalus species (unidentified) | 10 | 2018 |
| grasshopper, cricket or true cricket | Conocephalus dorsalis | Short-winged Conehead | 192 | 2021 |
| grasshopper, cricket or true cricket | Conocephalus fuscus | Long-winged Conehead | 293 | 2021 |
| lichen | Calicium glaucellum | a lichen | 2 | 1996 |
| lichen | Caloplaca | a Caloplaca species (unidentified) | 1 | 2009 |
| lichen | Caloplaca alociza | a lichen | 5 | 2018 |
| lichen | Caloplaca arcis | a lichen | 1 | 2011 |
| lichen | Caloplaca aurantia | a lichen | 26 | 2020 |
| lichen | Caloplaca aurea | a lichen | 1 | 2014 |
| lichen | Caloplaca austrocitrina | a lichen | 3 | 2014 |
| lichen | Caloplaca ceracea | a lichen | 1 | 2011 |
| lichen | Caloplaca cerina | a lichen | 1 | 2011 |
| lichen | Caloplaca cerinella | a lichen | 8 | 2014 |
| lichen | Caloplaca chalybaea | a lichen | 1 | 1991 |
| lichen | Caloplaca chlorina | a lichen | 1 | 2020 |
| lichen | Caloplaca chrysodeta | a lichen | 6 | 2008 |
| lichen | Caloplaca cirrochroa | a lichen | 6 | 2018 |
| lichen | Caloplaca citrina s. str. | a lichen | 42 | 2020 |
| lichen | Caloplaca crenularia | a lichen | 5 | 2010 |
| lichen | Caloplaca crenulatella | a lichen | 13 | 2016 |
| lichen | Caloplaca dalmatica | a lichen | 10 | 2010 |
| lichen | Caloplaca decipiens | a lichen | 5 | 2008 |
| lichen | Caloplaca dichroa | a lichen | 9 | 2018 |
| lichen | Caloplaca flavescens | a lichen | 70 | 2020 |
| lichen | Caloplaca flavocitrina | a lichen | 13 | 2018 |
| lichen | Caloplaca flavovirescens | a lichen | 2 | 2011 |
| lichen | Caloplaca granulosa | a lichen | 1 | 1991 |
| lichen | Caloplaca holocarpa s. str. | a lichen | 32 | 2020 |
| lichen | Caloplaca limonia | a lichen | 6 | 2011 |
| lichen | Caloplaca marina | a lichen | 2 | 2010 |
| lichen | Caloplaca marmorata | a lichen | 9 | 2018 |
| lichen | Caloplaca oasis | a lichen | 9 | 2018 |
| lichen | Caloplaca ochracea | a lichen | 11 | 2018 |
| lichen | Caloplaca saxicola | a lichen | 12 | 2011 |
| lichen | Caloplaca teicholyta | a lichen | 8 | 2011 |
| lichen | Caloplaca thallincola | a lichen | 4 | 2012 |
| lichen | Caloplaca variabilis | a lichen | 5 | 2018 |
| lichen | Caloplaca xantholyta | a lichen | 5 | 2005 |
| lichen | Candelaria concolor | a lichen | 1 | 2018 |
| lichen | Candelariella aurella | a lichen | 1 | 2009 |
| lichen | Candelariella aurella f. aurella | a lichen | 20 | 2014 |
| lichen | Candelariella medians f. medians | a lichen | 8 | 2020 |
| lichen | Candelariella reflexa | a lichen | 9 | 2020 |
| lichen | Candelariella vitellina | a lichen | 7 | 2020 |
| lichen | Candelariella vitellina f. flavovirella | a lichen | 1 | 1996 |
| lichen | Candelariella vitellina f. vitellina | a lichen | 37 | 2018 |
| lichen | Candelariella xanthostigma | a lichen | 1 | 2011 |
| lichen | Catillaria atomarioides | a lichen | 2 | 2014 |
| lichen | Catillaria chalybeia | a lichen | 1 | 2014 |
| lichen | Catillaria chalybeia var. chalybeia | a lichen | 12 | 2014 |
| lichen | Catillaria lenticularis | a lichen | 27 | 2018 |
| lichen | Catillaria nigroclavata | a lichen | 4 | 2016 |
| lichen | Chaenotheca brunneola | a lichen | 1 | 1988 |
| lichen | Chaenotheca chrysocephala | a lichen | 1 | 1988 |
| lichen | Chaenotheca ferruginea | a lichen | 6 | 2011 |
| lichen | Chaenotheca hispidula | a lichen | 1 | 1988 |
| lichen | Chrysothrix candelaris | a lichen | 3 | 1996 |
| lichen | Chrysothrix flavovirens | a lichen | 1 | 1988 |
| lichen | Cladonia | a Cladonia lichen (unidentified) | 9 | 2015 |
| lichen | Cladonia cervicornis | a lichen | 2 | 2009 |
| lichen | Cladonia chlorophaea s. lat. | a lichen | 7 | 2020 |
| lichen | Cladonia coniocraea | a lichen | 15 | 2020 |
| lichen | Cladonia convoluta | a lichen | 5 | 2016 |
| lichen | Cladonia crispata var. crispata | a lichen | 2 | 1998 |
| lichen | Cladonia fimbriata | a lichen | 19 | 2020 |
| lichen | Cladonia foliacea | a lichen | 2 | 2016 |
| lichen | Cladonia furcata | a lichen | 3 | 2020 |
| lichen | Cladonia furcata subsp. furcata | a lichen | 4 | 2016 |
| lichen | Cladonia furcata subsp. subrangiformis | a lichen | 4 | 2018 |
| lichen | Cladonia macilenta | a lichen | 1 | 1993 |
| lichen | Cladonia pocillum | a lichen | 8 | 2020 |
| lichen | Cladonia polydactyla var. polydactyla | a lichen | 2 | 2010 |
| lichen | Cladonia portentosa | Reindeer Moss | 10 | 2018 |
| lichen | Cladonia pyxidata | a lichen | 10 | 2018 |
| lichen | Cladonia ramulosa | a lichen | 1 | 2009 |
| lichen | Cladonia rangiformis | a lichen | 19 | 2020 |
| lichen | Cladonia squamosa s. lat. | a lichen | 2 | 2016 |
| lichen | Cladonia subcervicornis | a lichen | 3 | 2009 |
| lichen | Cladonia symphycarpa | a lichen | 1 | 1991 |
| lichen | Clauzadea chondrodes | a lichen | 2 | 2018 |
| lichen | Clauzadea immersa | a lichen | 9 | 2018 |
| lichen | Clauzadea metzleri | a lichen | 4 | 2018 |
| lichen | Clauzadea monticola | a lichen | 12 | 2021 |
| lichen | Cliostomum griffithii | a lichen | 5 | 2020 |
| lichen | Collema | a Collema species (unidentified) | 1 | 2019 |
| lichen | Collema auriforme | a lichen | 19 | 2021 |
| lichen | Collema crispum | a lichen | 5 | 2014 |
| lichen | Collema crispum var. crispum | a lichen | 11 | 2018 |
| lichen | Collema cristatum var. cristatum | a lichen | 3 | 2008 |
| lichen | Collema cristatum var. marginale | a lichen | 3 | 2018 |
| lichen | Collema fragile | a lichen | 1 | 1899 |
| lichen | Collema fuscovirens | a lichen | 6 | 2016 |
| lichen | Collema multipartitum | a lichen | 2 | 2005 |
| lichen | Collema tenax var. tenax | a lichen | 8 | 2020 |
| lichen | Cresponea premnea | a lichen | 4 | 1996 |
| liverwort | Calypogeia arguta | Notched Pouchwort | 3 | 2010 |
| liverwort | Calypogeia fissa | Common Pouchwort | 14 | 2019 |
| liverwort | Calypogeia muelleriana | Mueller's Pouchwort | 2 | 1994 |
| liverwort | Cephalozia | A Cephalozia liverwort (unidentified) | 1 | 1903 |
| liverwort | Cephalozia bicuspidata | Two-horned Pincerwort | 5 | 2015 |
| liverwort | Cephaloziella | A Cephaloziella liverwort (unidentified) | 1 | 2004 |
| liverwort | Cephaloziella divaricata | Common Threadwort | 2 | 2021 |
| liverwort | Cephaloziella hampeana | Hampe's Threadwort | 1 | 2007 |
| liverwort | Cephaloziella rubella | Red Threadwort | 1 | 1990 |
| liverwort | Chiloscyphus pallescens | St Winifrid's Other Moss | 3 | 2019 |
| liverwort | Chiloscyphus polyanthos | St Winifrid's Moss | 2 | 2021 |
| liverwort | Chiloscyphus polyanthos var. polyanthos | a liverwort | 1 | 1963 |
| liverwort | Cololejeunea minutissima | Minute Pouncewort | 12 | 2021 |
| liverwort | Conocephalum conicum | Great Scented Liverwort | 42 | 2022 |
| mammal | Capra hircus | Feral Goat | 2 | 2019 |
| mammal | Capreolus capreolus | Roe Deer | 2276 | 2023 |
| mammal | Cervidae | a deer (unidentified) | 131 | 2022 |
| mammal | Cervus elaphus | Red Deer | 18 | 2019 |
| mammal | Cervus nippon | Sika Deer | 3 | 1998 |
| mammal | Cricetidae or Muridae | a vole or mouse (unidentified) | 6 | 2015 |
| mammal | Cricetidae or Muridae or Myoxidae | a vole or mouse or dormouse (unidentified) | 1 | 2021 |
| mammal - bat | Chiroptera | a bat (unidentified) | 935 | 2022 |
| mammal - marine | Cetacea | a whale or dolphin (unidentified) | 1 | 1620 |
| mayfly | Caenis | a Caenis mayfly (unidentified) | 1 | 2004 |
| mayfly | Caenis horaria | a mayfly | 6 | 2012 |
| mayfly | Caenis luctuosa | Angler's Curse | 8 | 2004 |
| mayfly | Caenis macrura | a mayfly | 1 | 2010 |
| mayfly | Caenis rivulorum | a mayfly | 1 | 2021 |
| mayfly | Caenis robusta | a mayfly | 19 | 2013 |
| mayfly | Centroptilum luteolum | a mayfly | 2 | 1997 |
| mayfly | Cloeon dipterum | Pond Olive | 158 | 2021 |
| mayfly | Cloeon simile | a mayfly | 8 | 2013 |
| millipede | Chordeuma proximum/sylvestre | a Chordeuma millipede (unidentified) | 1 | 1998 |
| millipede | Cylindroiulus | a Cylindroiulus species (unidentified) | 2 | 2016 |
| millipede | Cylindroiulus caeruleocinctus | a julid snake millipede | 6 | 2013 |
| millipede | Cylindroiulus latestriatus | a julid snake millipede | 1 | 1995 |
| millipede | Cylindroiulus punctatus | Blunt-tailed Snake Millipede | 23 | 2018 |
| mollusc | Carychium | a herald snail | 3 | 2006 |
| mollusc | Carychium minimum | Short-toothed Herald Snail | 5 | 2004 |
| mollusc | Carychium tridentatum | a herald snail | 19 | 2006 |
| mollusc | Cecilioides (Cecilioides) acicula | Blind Snail | 4 | 2000 |
| mollusc | Cepaea | a Cepaea species (unidentified) | 3 | 2016 |
| mollusc | Cepaea (Cepaea) agg. | a cepaea snail | 3 | 2017 |
| mollusc | Cepaea (Cepaea) hortensis | White-lipped Snail | 370 | 2021 |
| mollusc | Cepaea (Cepaea) nemoralis | Brown Lipped Snail | 364 | 2022 |
| mollusc | Cepaea/Helix sp. | a Cepaea or Helix snail (unidentified) | 16 | 2009 |
| mollusc | Cerastoderma edule | Common Cockle | 4 | 2019 |
| mollusc | Cerastoderma glaucum | Lagoon Cockle | 3 | 1972 |
| mollusc | Cernuella (Cernuella) virgata | Banded Snail | 54 | 2021 |
| mollusc | Clausilia (Clausilia) bidentata | Two-toothed Door Snail | 97 | 2020 |
| mollusc | Cochlicella (Cochlicella) acuta | Pointed Snail | 11 | 2020 |
| mollusc | Cochlicella (Prietocella) barbara | a snail | 1 | 2019 |
| mollusc | Cochlicopa | a Cochlicopa species (unidentified) | 4 | 2019 |
| mollusc | Cochlicopa cf. lubrica or Cochlicopa cf. lubricella (unidentified) | Slippery Moss Snail or Least Slippery Snail (unidentified) | 1 | 2007 |
| mollusc | Cochlicopa cf. lubrica (sensu Anderson 2008) | Slippery Moss Snail | 85 | 2018 |
| mollusc | Cochlicopa cf. lubricella (sensu Anderson 2008) | Least Slippery Snail | 18 | 2014 |
| mollusc | Cochlicopa lubrica agg. | a mollusc | 4 | 2016 |
| mollusc | Cochlodina (Cochlodina) laminata | Plaited Door Snail | 67 | 2020 |
| mollusc | Columella aspera | a chrysalis snail | 1 | 1983 |
| mollusc | Columella edentula | a mollusc | 3 | 2020 |
| mollusc | Columella edentula agg. | a chrysalis snail | 2 | 2004 |
| mollusc | Cornu aspersum | Common Garden Snail | 447 | 2021 |
| mollusc | Crepidula fornicata | American Slipper Limpet | 2 | 2019 |
| moss | Calliergon | a Calliergon species (unidentified) | 1 | 2013 |
| moss | Calliergonella | a Calliergonella species (unidentified) | 2 | 2009 |
| moss | Calliergonella cuspidata | Pointed Spear-moss | 188 | 2021 |
| moss | Campyliadelphus chrysophyllus | Golden Feather-moss | 1 | 2017 |
| moss | Campylium protensum | a moss | 1 | 1963 |
| moss | Campylium stellatum (s.lat.) | Yellow Starry Feather-moss | 3 | 2020 |
| moss | Campylium stellatum (s.str.) | a yellow starry feather-moss | 1 | 1986 |
| moss | Campylopus flexuosus | Rusty Swan-neck Moss | 2 | 2009 |
| moss | Campylopus introflexus | Heath Star Moss | 28 | 2021 |
| moss | Campylopus pyriformis | Dwarf Swan-neck Moss | 2 | 2006 |
| moss | Campylopus shawii | Shaw's Swan-neck Moss | 2 | 1978 |
| moss | Ceratodon conicus | Scarce Redshank | 2 | 2019 |
| moss | Ceratodon purpureus | Redshank (moss) | 183 | 2021 |
| moss | Cheilothela chloropus | Rabbit Moss | 3 | 2015 |
| moss | Cirriphyllum crassinervium | Beech Feather-moss | 17 | 2017 |
| moss | Cirriphyllum piliferum | Hair-pointed Feather-moss | 32 | 2021 |
| moss | Climacium dendroides | Tree-moss | 2 | 2000 |
| moss | Cratoneuron filicinum | Fern-leaved Hook-moss | 33 | 2021 |
| moss | Cratoneuron filicinum (sensu lato) | a moss | 1 | 2013 |
| moss | Cryphaea heteromalla | Lateral Cryphaea | 115 | 2021 |
| moss | Ctenidium | a Ctenidium species (unidentified) | 1 | 2019 |
| moss | Ctenidium molluscum | Chalk Comb-moss | 57 | 2021 |
| moss | Ctenidium molluscum var. molluscum | a chalk comb-moss | 8 | 2003 |
| moss | Cynodontium bruntonii | Brunton's Dog-tooth | 1 | 1990 |
| moth or butterfly - butterfly | Callophrys rubi | Green Hairstreak | 631 | 2020 |
| moth or butterfly - butterfly | Celastrina argiolus | Holly Blue | 9096 | 2022 |
| moth or butterfly - butterfly | Celastrina argiolus britanna | a Holly Blue | 10 | 2013 |
| moth or butterfly - butterfly | Coenonympha pamphilus | Small Heath | 3344 | 2021 |
| moth or butterfly - butterfly | Colias croceus | Clouded Yellow | 1088 | 2022 |
| moth or butterfly - butterfly | Colias croceus form helice | Clouded Yellow (pale f.) | 4 | 2000 |
| moth or butterfly - butterfly | Colias hyale | Pale Clouded Yellow | 11 | 2000 |
| moth or butterfly - butterfly | Cupido minimus | Small Blue | 440 | 2022 |
| moth or butterfly - macro moth | Cabera | a Cabera species (unidentified) | 1 | 2016 |
| moth or butterfly - macro moth | Cabera exanthemata | Common Wave | 604 | 2022 |
| moth or butterfly - macro moth | Cabera pusaria | Common White Wave | 628 | 2022 |
| moth or butterfly - macro moth | Callimorpha dominula | Scarlet Tiger | 847 | 2022 |
| moth or butterfly - macro moth | Calliteara pudibunda | Pale Tussock | 907 | 2022 |
| moth or butterfly - macro moth | Calophasia lunula | Toadflax Brocade | 2 | 2017 |
| moth or butterfly - macro moth | Campaea margaritaria | Light Emerald | 1405 | 2022 |
| moth or butterfly - macro moth | Camptogramma bilineata | Yellow Shell | 1535 | 2022 |
| moth or butterfly - macro moth | Camptogramma bilineata subsp. bilineata | a Yellow Shell | 17 | 2011 |
| moth or butterfly - macro moth | Caradrina clavipalpis | Pale Mottled Willow | 2161 | 2022 |
| moth or butterfly - macro moth | Caradrina kadenii | a moth | 2 | 2022 |
| moth or butterfly - macro moth | Caradrina morpheus | Mottled Rustic | 1227 | 2022 |
| moth or butterfly - macro moth | Catarhoe cuculata | Royal Mantle | 10 | 2018 |
| moth or butterfly - macro moth | Catarhoe rubidata | Ruddy Carpet | 33 | 2020 |
| moth or butterfly - macro moth | Catocala fraxini | Clifden Nonpareil | 32 | 2022 |
| moth or butterfly - macro moth | Catocala nupta | Red Underwing | 321 | 2022 |
| moth or butterfly - macro moth | Catocala promissa | Light Crimson Underwing | 1 | 2020 |
| moth or butterfly - macro moth | Catocala sponsa | Dark Crimson Underwing | 1 | 2020 |
| moth or butterfly - macro moth | Cepphis advenaria | Little Thorn | 64 | 2020 |
| moth or butterfly - macro moth | Ceramica pisi | Broom Moth | 34 | 2020 |
| moth or butterfly - macro moth | Cerapteryx graminis | Antler | 27 | 2014 |
| moth or butterfly - macro moth | Cerastis rubricosa | Red Chestnut | 75 | 2020 |
| moth or butterfly - macro moth | Cerura vinula | Puss Moth | 179 | 2022 |
| moth or butterfly - macro moth | Charanyca trigrammica | Treble Lines | 1568 | 2022 |
| moth or butterfly - macro moth | Charissa obscurata | Annulet | 24 | 2014 |
| moth or butterfly - macro moth | Chesias legatella | Streak | 3 | 1996 |
| moth or butterfly - macro moth | Chesias rufata | Broom-tip | 1 | 1952 |
| moth or butterfly - macro moth | Chiasmia clathrata | Latticed Heath | 397 | 2022 |
| moth or butterfly - macro moth | Chiasmia clathrata clathrata | a Latticed Heath | 4 | 2010 |
| moth or butterfly - macro moth | Chilodes maritima | Silky Wainscot | 46 | 2020 |
| moth or butterfly - macro moth | Chloroclysta miata | Autumn Green Carpet | 28 | 2011 |
| moth or butterfly - macro moth | Chloroclysta siterata | Red-green Carpet | 439 | 2022 |
| moth or butterfly - macro moth | Chloroclystis v-ata | V-Pug | 1004 | 2022 |
| moth or butterfly - macro moth | Chrysodeixis chalcites | Golden Twin-spot | 1 | 1979 |
| moth or butterfly - macro moth | Cidaria fulvata | Barred Yellow | 361 | 2022 |
| moth or butterfly - macro moth | Cilix glaucata | Chinese Character | 650 | 2022 |
| moth or butterfly - macro moth | Cirrhia gilvago | Dusky-lemon Sallow | 21 | 2018 |
| moth or butterfly - macro moth | Cirrhia icteritia | Sallow (moth) | 223 | 2022 |
| moth or butterfly - macro moth | Cirrhia ocellaris | Pale-lemon Sallow | 2 | 2011 |
| moth or butterfly - macro moth | Cleorodes lichenaria | Brussels Lace | 114 | 2022 |
| moth or butterfly - macro moth | Clostera curtula | Chocolate-tip | 234 | 2022 |
| moth or butterfly - macro moth | Coenobia rufa | Small Rufous | 19 | 2021 |
| moth or butterfly - macro moth | Colocasia coryli | Nut-tree Tussock | 742 | 2022 |
| moth or butterfly - macro moth | Colostygia multistrigaria | Mottled Grey | 25 | 2021 |
| moth or butterfly - macro moth | Colostygia olivata | Beech-green Carpet | 12 | 2004 |
| moth or butterfly - macro moth | Colostygia pectinataria | Green Carpet | 1421 | 2022 |
| moth or butterfly - macro moth | Colotois pennaria | Feathered Thorn | 464 | 2022 |
| moth or butterfly - macro moth | Comibaena bajularia | Blotched Emerald | 25 | 2018 |
| moth or butterfly - macro moth | Conistra | a Conistra species (unidentified) | 1 | 2021 |
| moth or butterfly - macro moth | Conistra ligula | Dark Chestnut | 162 | 2022 |
| moth or butterfly - macro moth | Conistra rubiginea | Dotted Chestnut | 113 | 2022 |
| moth or butterfly - macro moth | Conistra vaccinii | Chestnut (moth) | 401 | 2022 |
| moth or butterfly - macro moth | Cosmia affinis | Lesser-spotted Pinion | 42 | 2020 |
| moth or butterfly - macro moth | Cosmia diffinis | White-spotted Pinion | 8 | 2022 |
| moth or butterfly - macro moth | Cosmia pyralina | Lunar-spotted Pinion | 106 | 2021 |
| moth or butterfly - macro moth | Cosmia trapezina | Dun-bar | 919 | 2022 |
| moth or butterfly - macro moth | Cosmorhoe ocellata | Purple Bar | 324 | 2022 |
| moth or butterfly - macro moth | Cossus cossus | Goat Moth | 9 | 1971 |
| moth or butterfly - macro moth | Craniophora ligustri | Coronet | 1389 | 2022 |
| moth or butterfly - macro moth | Crocallis elinguaria | Scalloped Oak | 2259 | 2022 |
| moth or butterfly - macro moth | Cryphia muralis form impar | Marbled Green f.impar (E & W England) | 12 | 2011 |
| moth or butterfly - macro moth | Cucullia absinthii | Wormwood (moth) | 6 | 2018 |
| moth or butterfly - macro moth | Cucullia chamomillae | Chamomile Shark | 17 | 2020 |
| moth or butterfly - macro moth | Cucullia lychnitis | Striped Lychnis | 1 | 1952 |
| moth or butterfly - macro moth | Cucullia umbratica | Shark | 223 | 2022 |
| moth or butterfly - macro moth | Cucullia verbasci | Mullein Moth | 250 | 2022 |
| moth or butterfly - macro moth | Cybosia mesomella | Four-dotted Footman | 8 | 2022 |
| moth or butterfly - macro moth | Cyclophora albipunctata | Birch Mocha | 6 | 2008 |
| moth or butterfly - macro moth | Cyclophora annularia | Mocha | 323 | 2022 |
| moth or butterfly - macro moth | Cyclophora linearia | Clay Triple-lines | 170 | 2022 |
| moth or butterfly - macro moth | Cyclophora pendularia | Dingy Mocha | 2 | 1965 |
| moth or butterfly - macro moth | Cyclophora porata | False Mocha | 2 | 1940 |
| moth or butterfly - macro moth | Cyclophora punctaria | Maiden's Blush | 288 | 2022 |
| moth or butterfly - macro moth | Cyclophora puppillaria | Blair's Mocha | 4 | 2014 |
| moth or butterfly - macro moth | Cymatophorina diluta hartwiegi | Oak Lutestring | 9 | 1991 |
| moth or butterfly - micro moth | Cacoecimorpha pronubana | Carnation Tortrix | 112 | 2022 |
| moth or butterfly - micro moth | Calamotropha paludella | a pyralid moth | 106 | 2022 |
| moth or butterfly - micro moth | Callisto denticulella | a micro-moth | 16 | 2020 |
| moth or butterfly - micro moth | Caloptilia | a Caloptilia micro-moth (unidentified) | 7 | 2017 |
| moth or butterfly - micro moth | Caloptilia alchimiella | Yellow-triangle Slender | 22 | 2020 |
| moth or butterfly - micro moth | Caloptilia azaleella | Azalea Leaf Miner | 7 | 2020 |
| moth or butterfly - micro moth | Caloptilia betulicola | a micro-moth | 10 | 2021 |
| moth or butterfly - micro moth | Caloptilia cuculipennella | a micro-moth | 7 | 2020 |
| moth or butterfly - micro moth | Caloptilia elongella | a micro-moth | 36 | 2022 |
| moth or butterfly - micro moth | Caloptilia falconipennella | a micro-moth | 6 | 2022 |
| moth or butterfly - micro moth | Caloptilia hauderi | a micro-moth | 2 | 2011 |
| moth or butterfly - micro moth | Caloptilia hemidactylella | a micro-moth | 3 | 2020 |
| moth or butterfly - micro moth | Caloptilia populetorum | a micro-moth | 13 | 2020 |
| moth or butterfly - micro moth | Caloptilia robustella | a micro-moth | 30 | 2022 |
| moth or butterfly - micro moth | Caloptilia rufipennella | a micro-moth | 77 | 2022 |
| moth or butterfly - micro moth | Caloptilia semifascia | a micro-moth | 191 | 2022 |
| moth or butterfly - micro moth | Caloptilia stigmatella | a micro-moth | 73 | 2021 |
| moth or butterfly - micro moth | Calybites phasianipennella | a micro-moth | 1 | 2018 |
| moth or butterfly - micro moth | Cameraria ohridella | Horse-Chestnut Leaf-miner | 377 | 2022 |
| moth or butterfly - micro moth | Capperia britanniodactylus | a plume moth | 12 | 2015 |
| moth or butterfly - micro moth | Capua vulgana | Common Twist | 35 | 2019 |
| moth or butterfly - micro moth | Carcina quercana | Long-horned Flat-body | 656 | 2022 |
| moth or butterfly - micro moth | Carpatolechia alburnella | a micro-moth | 4 | 2015 |
| moth or butterfly - micro moth | Carpatolechia decorella | a micro-moth | 3 | 2020 |
| moth or butterfly - micro moth | Carpatolechia fugitivella | a micro-moth | 4 | 2014 |
| moth or butterfly - micro moth | Carpatolechia proximella | a micro-moth | 3 | 2019 |
| moth or butterfly - micro moth | Caryocolum | a Caryocolum species (unidentified) | 2 | 2021 |
| moth or butterfly - micro moth | Caryocolum blandella | a micro-moth | 2 | 1994 |
| moth or butterfly - micro moth | Caryocolum blandulella | a micro-moth | 1 | 1994 |
| moth or butterfly - micro moth | Caryocolum viscariella | a micro-moth | 3 | 2020 |
| moth or butterfly - micro moth | Cataclysta lemnata | Small China-mark | 341 | 2022 |
| moth or butterfly - micro moth | Cataclysta sp. or Elophila sp. (unditentified) | a china-mark moth (unidentified) | 3 | 2011 |
| moth or butterfly - micro moth | Catoptria falsella | a pyralid moth | 45 | 2022 |
| moth or butterfly - micro moth | Catoptria margaritella | Silver-stripe Grass-veneer | 2 | 2014 |
| moth or butterfly - micro moth | Catoptria pinella | a pyralid moth | 74 | 2022 |
| moth or butterfly - micro moth | Cauchas fibulella | a longhorn moth | 42 | 2022 |
| moth or butterfly - micro moth | Cauchas rufimitrella | a longhorn moth | 70 | 2021 |
| moth or butterfly - micro moth | Cedestis gysseleniella | a micro-moth | 2 | 2019 |
| moth or butterfly - micro moth | Cedestis subfasciella | a micro-moth | 8 | 2021 |
| moth or butterfly - micro moth | Celypha aurofasciana | a tortrix moth | 3 | 2014 |
| moth or butterfly - micro moth | Celypha cespitana | a tortrix moth | 12 | 2021 |
| moth or butterfly - micro moth | Celypha lacunana | Common Marble | 1924 | 2022 |
| moth or butterfly - micro moth | Celypha rivulana | a tortrix moth | 2 | 2005 |
| moth or butterfly - micro moth | Celypha striana | a tortrix moth | 1518 | 2022 |
| moth or butterfly - micro moth | Celypha woodiana | Mistletoe Marble | 7 | 2009 |
| moth or butterfly - micro moth | Chilo phragmitella | a pyralid moth | 18 | 2020 |
| moth or butterfly - micro moth | Chionodes fumatella | a micro-moth | 1 | 2001 |
| moth or butterfly - micro moth | Choreutis pariana | Apple Leaf Skeletoniser | 21 | 2021 |
| moth or butterfly - micro moth | Choristoneura diversana | a tortrix moth | 2 | 2014 |
| moth or butterfly - micro moth | Choristoneura hebenstreitella | a tortrix moth | 1 | 1994 |
| moth or butterfly - micro moth | Chrysoclista linneella | a micro-moth | 9 | 2019 |
| moth or butterfly - micro moth | Chrysoesthia drurella | a micro-moth | 1 | 2013 |
| moth or butterfly - micro moth | Chrysoesthia sexguttella | a micro-moth | 6 | 2020 |
| moth or butterfly - micro moth | Chrysoteuchia culmella | Garden Grass-veneer | 3304 | 2022 |
| moth or butterfly - micro moth | Clavigesta purdeyi | Pine Leaf-mining Moth | 12 | 2020 |
| moth or butterfly - micro moth | Clepsis consimilana | Privet Twist | 475 | 2022 |
| moth or butterfly - micro moth | Clepsis spectrana | a tortrix moth | 180 | 2020 |
| moth or butterfly - micro moth | Cnephasia | a tortrix moth (unidentified) | 141 | 2022 |
| moth or butterfly - micro moth | Cnephasia asseclana | Flax Tortrix | 149 | 2022 |
| moth or butterfly - micro moth | Cnephasia communana | a tortrix moth | 29 | 2022 |
| moth or butterfly - micro moth | Cnephasia conspersana | a tortrix moth | 6 | 2022 |
| moth or butterfly - micro moth | Cnephasia incertana | Light Grey Tortrix | 145 | 2022 |
| moth or butterfly - micro moth | Cnephasia longana | a tortrix moth | 7 | 2019 |
| moth or butterfly - micro moth | Cnephasia pasiuana | a tortrix moth | 3 | 2005 |
| moth or butterfly - micro moth | Cnephasia stephensiana | Grey Tortrix | 259 | 2022 |
| moth or butterfly - micro moth | Cochylidia implicitana | a micro-moth | 5 | 2018 |
| moth or butterfly - micro moth | Cochylidia rupicola | a micro-moth | 11 | 2014 |
| moth or butterfly - micro moth | Cochylimorpha straminea | Straw Conch | 68 | 2022 |
| moth or butterfly - micro moth | Cochylis atricapitana | a micro-moth | 153 | 2022 |
| moth or butterfly - micro moth | Cochylis dubitana | a micro-moth | 21 | 2018 |
| moth or butterfly - micro moth | Cochylis flaviciliana | a micro-moth | 2 | 1996 |
| moth or butterfly - micro moth | Cochylis hybridella | a micro-moth | 75 | 2021 |
| moth or butterfly - micro moth | Cochylis molliculana | a tortrix moth | 60 | 2021 |
| moth or butterfly - micro moth | Cochylis nana | a micro-moth | 7 | 2020 |
| moth or butterfly - micro moth | Cochylis roseana | a micro-moth | 66 | 2018 |
| moth or butterfly - micro moth | Coleophora | a Coleophora micro-moth (unidentified) | 33 | 2022 |
| moth or butterfly - micro moth | Coleophora adjunctella | a micro-moth | 1 | 2011 |
| moth or butterfly - micro moth | Coleophora adspersella | a micro-moth | 2 | 2014 |
| moth or butterfly - micro moth | Coleophora albella | a micro-moth | 1 | 1908 |
| moth or butterfly - micro moth | Coleophora albicosta | a micro-moth | 7 | 2014 |
| moth or butterfly - micro moth | Coleophora albidella | a micro-moth | 8 | 2022 |
| moth or butterfly - micro moth | Coleophora albitarsella | a micro-moth | 23 | 2022 |
| moth or butterfly - micro moth | Coleophora alcyonipennella | Small Clover Case-bearer | 5 | 2019 |
| moth or butterfly - micro moth | Coleophora alcyonipennella/frischella | a moth | 5 | 2021 |
| moth or butterfly - micro moth | Coleophora alticolella | Common Rush Case-bearer | 13 | 2020 |
| moth or butterfly - micro moth | Coleophora anatipennella | Pistol Case-bearer | 8 | 2015 |
| moth or butterfly - micro moth | Coleophora argentula | a micro-moth | 6 | 2022 |
| moth or butterfly - micro moth | Coleophora artemisicolella | a micro-moth | 1 | 2021 |
| moth or butterfly - micro moth | Coleophora asteris | a micro-moth | 1 | 2012 |
| moth or butterfly - micro moth | Coleophora atriplicis | a micro-moth | 3 | 2018 |
| moth or butterfly - micro moth | Coleophora badiipennella | a micro-moth | 3 | 2020 |
| moth or butterfly - micro moth | Coleophora betulella | a micro-moth | 4 | 2014 |
| moth or butterfly - micro moth | Coleophora binderella | a micro-moth | 2 | 2021 |
| moth or butterfly - micro moth | Coleophora caespititiella | a micro-moth | 10 | 2022 |
| moth or butterfly - micro moth | Coleophora conyzae | a micro-moth | 4 | 2013 |
| moth or butterfly - micro moth | Coleophora coracipennella | a micro-moth | 3 | 2020 |
| moth or butterfly - micro moth | Coleophora currucipennella | a micro-moth | 3 | 2006 |
| moth or butterfly - micro moth | Coleophora deauratella | a micro-moth | 27 | 2022 |
| moth or butterfly - micro moth | Coleophora discordella | a micro-moth | 4 | 2016 |
| moth or butterfly - micro moth | Coleophora flavipennella | Tipped Oak Case-bearer | 16 | 2021 |
| moth or butterfly - micro moth | Coleophora follicularis | a micro-moth | 6 | 2019 |
| moth or butterfly - micro moth | Coleophora frischella | a moth | 1 | 2008 |
| moth or butterfly - micro moth | Coleophora glaucicolella | a micro-moth | 7 | 2021 |
| moth or butterfly - micro moth | Coleophora gryphipennella | a micro-moth | 18 | 2021 |
| moth or butterfly - micro moth | Coleophora ibipennella | a micro-moth | 5 | 2013 |
| moth or butterfly - micro moth | Coleophora juncicolella | a micro-moth | 1 | 1908 |
| moth or butterfly - micro moth | Coleophora kuehnella | a micro-moth | 1 | 2010 |
| moth or butterfly - micro moth | Coleophora laricella | Larch Case-bearer | 3 | 2016 |
| moth or butterfly - micro moth | Coleophora limosipennella | a micro-moth | 12 | 2021 |
| moth or butterfly - micro moth | Coleophora lineolea | a micro-moth | 31 | 2022 |
| moth or butterfly - micro moth | Coleophora lixella | a micro-moth | 4 | 1999 |
| moth or butterfly - micro moth | Coleophora lusciniaepennella | a micro-moth | 11 | 2014 |
| moth or butterfly - micro moth | Coleophora lutarea | a micro-moth | 6 | 2019 |
| moth or butterfly - micro moth | Coleophora lutipennella | a micro-moth | 16 | 2022 |
| moth or butterfly - micro moth | Coleophora lutipennella/flavipennella | a micro-moth (Coleophora lutipennella or Coleophora flavipennella undetermined) | 1 | 2002 |
| moth or butterfly - micro moth | Coleophora maritimella | a micro-moth | 1 | 1997 |
| moth or butterfly - micro moth | Coleophora mayrella | a micro-moth | 47 | 2022 |
| moth or butterfly - micro moth | Coleophora milvipennis | a micro-moth | 3 | 2021 |
| moth or butterfly - micro moth | Coleophora ochrea | a micro-moth | 21 | 2020 |
| moth or butterfly - micro moth | Coleophora otidipennella | a micro-moth | 4 | 2021 |
| moth or butterfly - micro moth | Coleophora paripennella | a micro-moth | 7 | 2021 |
| moth or butterfly - micro moth | Coleophora peribenanderi | Pale Thistle Case-bearer | 15 | 2020 |
| moth or butterfly - micro moth | Coleophora potentillae | a micro-moth | 5 | 2016 |
| moth or butterfly - micro moth | Coleophora prunifoliae | a micro-moth | 2 | 1985 |
| moth or butterfly - micro moth | Coleophora pyrrhulipennella | a micro-moth | 2 | 2016 |
| moth or butterfly - micro moth | Coleophora salicorniae | a micro-moth | 2 | 2011 |
| moth or butterfly - micro moth | Coleophora saturatella | a micro-moth | 2 | 2016 |
| moth or butterfly - micro moth | Coleophora saxicolella | a micro-moth | 12 | 2022 |
| moth or butterfly - micro moth | Coleophora serratella | Common Case-bearer | 24 | 2021 |
| moth or butterfly - micro moth | Coleophora spinella | Apple & Plum Case-bearer | 14 | 2020 |
| moth or butterfly - micro moth | Coleophora sternipennella | a micro-moth | 4 | 2022 |
| moth or butterfly - micro moth | Coleophora striatipennella | a micro-moth | 2 | 2016 |
| moth or butterfly - micro moth | Coleophora sylvaticella | a micro-moth | 1 | 2003 |
| moth or butterfly - micro moth | Coleophora taeniipennella | a micro-moth | 4 | 2014 |
| moth or butterfly - micro moth | Coleophora trifolii | Large Clover Case-bearer | 60 | 2022 |
| moth or butterfly - micro moth | Coleophora trochilella | a micro-moth | 1 | 1908 |
| moth or butterfly - micro moth | Coleophora versurella | a micro-moth | 4 | 2022 |
| moth or butterfly - micro moth | Coleophora violacea | a micro-moth | 1 | 1994 |
| moth or butterfly - micro moth | Coleophora virgaureae | a micro-moth | 3 | 2003 |
| moth or butterfly - micro moth | Commophila aeneana | a micro-moth | 3 | 2005 |
| moth or butterfly - micro moth | Coptotriche marginea | Bordered Carl | 140 | 2022 |
| moth or butterfly - micro moth | Cosmopterix lienigiella | a micro-moth | 1 | 2015 |
| moth or butterfly - micro moth | Cosmopterix pulchrimella | a moth | 1 | 2010 |
| moth or butterfly - micro moth | Crambinae | a Crambinae species (unidentified) | 2 | 2014 |
| moth or butterfly - micro moth | Crambus | a Crambus species (unidentified) | 1 | 1991 |
| moth or butterfly - micro moth | Crambus lathoniellus | Hook-streak Grass-veneer | 504 | 2022 |
| moth or butterfly - micro moth | Crambus pascuella | a pyralid moth | 152 | 2022 |
| moth or butterfly - micro moth | Crambus perlella | Satin Grass-veneer | 1189 | 2022 |
| moth or butterfly - micro moth | Crambus pratella | a pyralid moth | 6 | 2017 |
| moth or butterfly - micro moth | Crassa tinctella | a micro-moth | 2 | 2009 |
| moth or butterfly - micro moth | Crassa unitella | a micro-moth | 209 | 2022 |
| moth or butterfly - micro moth | Crocidosema plebejana | a tortrix moth | 15 | 2022 |
| moth or butterfly - micro moth | Crombrugghia laetus | a plume moth | 2 | 2019 |
| moth or butterfly - micro moth | Cryptoblabes bistriga | a pyralid moth | 27 | 2021 |
| moth or butterfly - micro moth | Cryptoblabes gnidiella | a pyralid moth | 1 | 2002 |
| moth or butterfly - micro moth | Cydalima perspectalis | Box Tree Moth | 295 | 2022 |
| moth or butterfly - micro moth | Cydia | a Cydia species (unidentified) | 1 | 2010 |
| moth or butterfly - micro moth | Cydia amplana | a tortrix moth | 9 | 2021 |
| moth or butterfly - micro moth | Cydia coniferana | a tortrix moth | 1 | 2000 |
| moth or butterfly - micro moth | Cydia fagiglandana | a tortrix moth | 50 | 2022 |
| moth or butterfly - micro moth | Cydia nigricana | Pea Moth | 31 | 2021 |
| moth or butterfly - micro moth | Cydia pomonella | Codling Moth | 785 | 2022 |
| moth or butterfly - micro moth | Cydia servillana | a tortrix moth | 2 | 2010 |
| moth or butterfly - micro moth | Cydia splendana | Marbled Piercer | 308 | 2022 |
| moth or butterfly - micro moth | Cydia strobilella | a tortrix moth | 1 | 2019 |
| moth or butterfly - micro moth | Cydia ulicetana | Grey Gorse Piercer | 80 | 2022 |
| plant | Cakile maritima | Sea Rocket | 28 | 2020 |
| plant | Cakile maritima subsp. integrifolia | a crucifer | 17 | 1998 |
| plant | Calamagrostis epigejos | Wood Small-reed | 121 | 2018 |
| plant | Calendula arvensis | Field Marigold | 5 | 2017 |
| plant | Calendula officinalis | pot Marigold | 57 | 2020 |
| plant | Calla palustris | Bog Arum | 1 | 1984 |
| plant | Callitriche | a water-starwort (unidentified) | 375 | 2018 |
| plant | Callitriche aggregate | a flowering plant | 38 | 2013 |
| plant | Callitriche hamulata | Intermediate Water-Starwort | 8 | 2004 |
| plant | Callitriche obtusangula | Blunt-fruited Water-starwort | 65 | 2016 |
| plant | Callitriche platycarpa | Various-leaved Water-starwort | 40 | 2013 |
| plant | Callitriche stagnalis | Common Water-starwort | 221 | 2016 |
| plant | Callitriche stagnalis (sensu lato) | Common Water-starwort sens.lat. | 26 | 2006 |
| plant | Callitriche truncata | Short-leaved Water-starwort | 5 | 1999 |
| plant | Callitriche truncata subsp. occidentalis | a flowering plant | 2 | 1962 |
| plant | Calluna | a Calluna species (unidentified) | 1 | 2016 |
| plant | Calluna vulgaris | Heather | 121 | 2019 |
| plant | Calocedrus decurrens | Californian Incense-cedar | 12 | 2015 |
| plant | Caltha palustris | Marsh Marigold | 496 | 2021 |
| plant | Calystegia | a Calystegia species (unidentified) | 42 | 2021 |
| plant | Calystegia pulchra | Hairy Bindweed | 10 | 2011 |
| plant | Calystegia sepium | Hedge Bindweed | 1167 | 2021 |
| plant | Calystegia sepium (sens.lat.) | Hedge Bindweed (sens.lat.) | 10 | 2014 |
| plant | Calystegia sepium subsp. sepium | Great Bindweed | 1703 | 2017 |
| plant | Calystegia sepium x silvatica = C. x lucana | a bindweed | 35 | 2011 |
| plant | Calystegia silvatica | Large Bindweed | 719 | 2020 |
| plant | Calystegia silvatica subsp. disjuncta | a flowering plant | 1 | 2015 |
| plant | Calystegia silvatica var. quinquepartita | a bindweed | 1 | 2013 |
| plant | Calystegia soldanella | Sea Bindweed | 8 | 2008 |
| plant | Calystegia sp. or Convolvulus sp. (unidentified bindweed) | a bindweed (unidentified) | 60 | 2021 |
| plant | Calystegia subsp. sepium forma colorata | a bindweed | 1 | 1999 |
| plant | Camassia | a Camassia species (unidentified) | 1 | 2012 |
| plant | Camassia leichtlinii | a flowering plant | 2 | 2019 |
| plant | Camelina alyssum | a gold-of-pleasure | 1 | 1937 |
| plant | Camelina microcarpa | Lesser Gold-of-pleasure | 4 | 1961 |
| plant | Camelina sativa | Gold-of-pleasure | 6 | 2009 |
| plant | Campanula | a bellflower (unidentified) | 12 | 2017 |
| plant | Campanula alliariifolia | Cornish Bellflower | 3 | 2000 |
| plant | Campanula glomerata | Clustered Bellflower | 86 | 2014 |
| plant | Campanula latifolia | Giant Bellflower | 9 | 2016 |
| plant | Campanula medium | Canterbury-bell | 1 | 1984 |
| plant | Campanula patula | Spreading Bellflower | 20 | 2011 |
| plant | Campanula persicifolia | Peach-leaved Bellflower | 4 | 2010 |
| plant | Campanula portenschlagiana | Adria Bellflower | 349 | 2020 |
| plant | Campanula poscharskyana | Trailing Bellflower | 324 | 2020 |
| plant | Campanula rapunculoides | Creeping Bellflower | 9 | 2018 |
| plant | Campanula rotundifolia | Harebell | 388 | 2019 |
| plant | Campanula trachelium | Nettle-leaved Bellflower | 207 | 2019 |
| plant | Cannabis sativa | Hemp | 19 | 2014 |
| plant | Capsella bursa-pastoris | Shepherd's-purse | 3382 | 2021 |
| plant | Capsicum annuum | Sweet Pepper | 2 | 1930 |
| plant | Caragana | a Caragana species (unidentified) | 1 | 2009 |
| plant | Cardamine | a Cardamine crucifer (unidentified) | 27 | 2018 |
| plant | Cardamine amara | Large Bitter-cress | 6 | 2018 |
| plant | Cardamine bulbifera | Coralroot | 17 | 2019 |
| plant | Cardamine corymbosa | a flowering plant | 5 | 2016 |
| plant | Cardamine flexuosa | Wavy Bitter-cress | 1327 | 2021 |
| plant | Cardamine hirsuta | Hairy Bitter-cress | 2431 | 2021 |
| plant | Cardamine impatiens | Narrow-leaved Bitter-cress | 49 | 2019 |
| plant | Cardamine pratensis | Cuckoo-flower | 2218 | 2021 |
| plant | Cardamine pratensis x flexuosa = C. x fringsii | a bitter-cress | 2 | 2000 |
| plant | Carduus crispus | Welted Thistle | 875 | 2021 |
| plant | Carduus crispus subsp. multiflorus | Broad-winged Thistle | 6 | 2016 |
| plant | Carduus crispus x nutans = C. x stangii | a thistle | 2 | 1995 |
| plant | Carduus hamulosus | a flowering plant | 1 | 1938 |
| plant | Carduus macrocephalus | Giant Thistle | 1 | 1938 |
| plant | Carduus nutans | Musk Thistle | 441 | 2021 |
| plant | Carduus pycnocephalus | Plymouth Thistle | 4 | 1937 |
| plant | Carduus tenuiflorus | Slender Thistle | 48 | 2014 |
| plant | Carex | a sedge (unidentified) | 503 | 2022 |
| plant | Carex acuta | Slender Tufted-sedge | 17 | 2011 |
| plant | Carex acuta x elata = C. x prolixa | a sedge | 1 | 1913 |
| plant | Carex acutiformis | Lesser Pond-sedge | 314 | 2019 |
| plant | Carex arenaria | Sand Sedge | 71 | 2019 |
| plant | Carex binervis | Green-ribbed Sedge | 3 | 2015 |
| plant | Carex caryophyllea | Spring Sedge | 461 | 2019 |
| plant | Carex comans | New Zealand Hair Sedge | 1 | 2017 |
| plant | Carex digitata | Fingered Sedge | 24 | 2012 |
| plant | Carex distans | Distant Sedge | 69 | 2015 |
| plant | Carex disticha | Brown Sedge | 151 | 2019 |
| plant | Carex divisa | Divided Sedge | 2 | 1921 |
| plant | Carex divulsa | Grey Sedge | 420 | 2021 |
| plant | Carex divulsa subsp. divulsa | a grey sedge | 143 | 2019 |
| plant | Carex divulsa subsp. leersii | Leers' Sedge | 6 | 2016 |
| plant | Carex echinata | Star Sedge | 53 | 2019 |
| plant | Carex elata | Tufted Sedge | 14 | 2009 |
| plant | Carex extensa | Long-bracted Sedge | 56 | 2017 |
| plant | Carex flacca | Glaucous Sedge | 2531 | 2021 |
| plant | Carex flava × hostiana | a sedge | 1 | 1921 |
| plant | Carex hirta | Hairy Sedge | 1560 | 2020 |
| plant | Carex hostiana | Tawny Sedge | 49 | 2019 |
| plant | Carex hostiana x viridula = C. x fulva | a sedge | 1 | 1998 |
| plant | Carex humilis | Dwarf Sedge | 80 | 2013 |
| plant | Carex laevigata | Smooth-stalked Sedge | 10 | 2011 |
| plant | Carex leporina | Oval Sedge | 205 | 2019 |
| plant | Carex montana | Soft-leaved Sedge | 7 | 2008 |
| plant | Carex muricata | Prickly Sedge | 3 | 2004 |
| plant | Carex muricata subsp. pairae | a Prickly Sedge | 16 | 2012 |
| plant | Carex nigra | Common Sedge | 186 | 2018 |
| plant | Carex otrubae | False Fox-sedge | 1390 | 2020 |
| plant | Carex otrubae x remota = C. x pseudoaxillaris | a sedge | 3 | 1992 |
| plant | Carex pallescens | Pale Sedge | 22 | 2010 |
| plant | Carex panicea | Carnation Sedge | 257 | 2019 |
| plant | Carex paniculata | Greater Tussock-sedge | 10 | 2006 |
| plant | Carex pendula | Pendulous Sedge | 1960 | 2022 |
| plant | Carex pilulifera | Pill Sedge | 43 | 2019 |
| plant | Carex pseudocyperus | Cyperus Sedge | 199 | 2018 |
| plant | Carex pulicaris | Flea Sedge | 46 | 2019 |
| plant | Carex remota | Remote Sedge | 739 | 2020 |
| plant | Carex riparia | Great Pond-sedge | 499 | 2020 |
| plant | Carex rostrata | Bottle Sedge | 18 | 2018 |
| plant | Carex rupestris | Rock Sedge | 1 | 1989 |
| plant | Carex spicata | Spiked Sedge | 425 | 2019 |
| plant | Carex strigosa | Thin-spiked Wood-sedge | 190 | 2020 |
| plant | Carex sylvatica | Wood-sedge | 1584 | 2021 |
| plant | Carex vesicaria | Bladder-sedge | 7 | 2011 |
| plant | Carex viridula | Yellow Sedge | 5 | 2012 |
| plant | Carex viridula subsp. brachyrrhyncha | Long-stalked Yellow Sedge | 39 | 2018 |
| plant | Carex viridula subsp. oedocarpa | Common Yellow Sedge | 137 | 2018 |
| plant | Carex viridula subsp. viridula | Small-fruited Yellow Sedge | 2 | 2004 |
| plant | Carex vulpinoidea | American Fox-sedge | 1 | 1932 |
| plant | Carlina vulgaris | Carline Thistle | 318 | 2019 |
| plant | Carpinus | a Carpinus species (unidentified) | 4 | 2018 |
| plant | Carpinus betulus | Hornbeam | 616 | 2021 |
| plant | Carrichtera annua | a flowering plant | 2 | 2013 |
| plant | Carthamus lanatus | Downy Safflower | 2 | 1937 |
| plant | Carthamus oxyacanthus | a flowering plant | 2 | 1938 |
| plant | Carthamus tinctorius | Safflower | 1 | 2010 |
| plant | Carum carvi | Caraway | 8 | 2013 |
| plant | Castanea | a Castanea species (unidentified) | 2 | 2009 |
| plant | Castanea sativa | Sweet Chestnut | 522 | 2020 |
| plant | Catabrosa aquatica | Whorl-grass | 41 | 2013 |
| plant | Catalpa | a catalpa (unidentified) | 17 | 2000 |
| plant | Catalpa bignonioides | Indian Bean-tree | 6 | 2015 |
| plant | Catapodium marinum | Sea Fern-grass | 73 | 2019 |
| plant | Catapodium rigidum | Fern-grass | 431 | 2020 |
| plant | Caucalis platycarpos | Small Bur-parsley | 7 | 1939 |
| plant | Ceanothus | a ceanothus shrub (unidentified) | 1 | 2016 |
| plant | Cedrus | a cedar (unidentified) | 14 | 2020 |
| plant | Cedrus atlantica | Atlas Cedar | 133 | 2019 |
| plant | Cedrus deodara | Deodar | 71 | 2016 |
| plant | Cedrus libani | Cedar of Lebanon | 78 | 2020 |
| plant | Celosia trigyna | a flowering plant | 1 | 1928 |
| plant | Celtis occidentalis | Common Hackberry | 1 | 2015 |
| plant | Centaurea | a knapweed or cornflower (unidentified) | 60 | 2022 |
| plant | Centaurea calcitrapa | Red Star-thistle | 1 | 1926 |
| plant | Centaurea cyanus | Cornflower | 48 | 2019 |
| plant | Centaurea debeauxii | a flowering plant | 7 | 2014 |
| plant | Centaurea hyalolepis | a flowering plant | 2 | 1938 |
| plant | Centaurea iberica | a flowering plant | 2 | 1939 |
| plant | Centaurea jacea | Brown Knapweed | 4 | 2021 |
| plant | Centaurea maculosa | a flowering plant | 2 | 1930 |
| plant | Centaurea montana | Perennial Cornflower | 31 | 2019 |
| plant | Centaurea nigra sens. lat. (=nigra/debauxii) | Common Knapweed | 4420 | 2022 |
| plant | Centaurea nigra subsp. nigra | a common knapweed | 1 | 2021 |
| plant | Centaurea nigra var. nemoralis | a flowering plant | 2 | 1992 |
| plant | Centaurea nigra x jacea = C. x moncktonii | Hybrid Knapweed | 1 | 2000 |
| plant | Centaurea paniculata | Jersey Knapweed | 1 | 1934 |
| plant | Centaurea scabiosa | Greater Knapweed | 890 | 2021 |
| plant | Centaurea solstitialis | Yellow Star-thistle | 1 | 1956 |
| plant | Centaurium | a Centaury (unidentified) | 8 | 2015 |
| plant | Centaurium erythraea | Common Centaury | 1028 | 2021 |
| plant | Centaurium erythraea var. erythraea | a flowering plant | 1 | 1988 |
| plant | Centaurium littorale | Seaside Centaury | 3 | 1956 |
| plant | Centaurium pulchellum | Lesser Centaury | 24 | 2008 |
| plant | Centranthus ruber | Red Valerian | 1390 | 2021 |
| plant | Centunculus minimus | Chaffweed | 1 | 1915 |
| plant | Cephalanthera damasonium | White Helleborine | 40 | 2021 |
| plant | Cephalanthera longifolia | Narrow-leaved Helleborine | 3 | 1915 |
| plant | Cephalaria gigantea | Giant Scabious | 3 | 2008 |
| plant | Cephalaria syriaca | a flowering plant | 1 | 1931 |
| plant | Cerastium | a mouse-ear (unidentified) | 12 | 2017 |
| plant | Cerastium arvense | Field Mouse-ear | 18 | 2010 |
| plant | Cerastium diffusum | Sea Mouse-ear | 91 | 2016 |
| plant | Cerastium fontanum | Common Mouse-ear | 5290 | 2022 |
| plant | Cerastium fontanum subsp. holosteoides | a common mouse-ear | 36 | 2004 |
| plant | Cerastium fontanum subsp. vulgare | a common mouse-ear | 4 | 2016 |
| plant | Cerastium glomeratum | Sticky Mouse-ear | 1307 | 2020 |
| plant | Cerastium pumilum | Dwarf Mouse-ear | 80 | 2016 |
| plant | Cerastium semidecandrum | Little Mouse-ear | 138 | 2018 |
| plant | Cerastium tomentosum | Snow-in-summer | 246 | 2020 |
| plant | Ceratocapnos claviculata | Climbing Corydalis | 22 | 2011 |
| plant | Ceratochloa carinata | California Brome | 1 | 2010 |
| plant | Ceratochloa cathartica | Rescue Brome | 7 | 2015 |
| plant | Ceratophyllaceae | a Ceratophyllaceae species (unidentified) | 3 | 1988 |
| plant | Ceratophyllum | a Ceratophyllum species (unidentified) | 5 | 2014 |
| plant | Ceratophyllum demersum | Rigid Hornwort | 296 | 2019 |
| plant | Ceratophyllum submersum | Soft Hornwort | 55 | 2013 |
| plant | Cercidiphyllum | a Cercidiphyllum species (unidentified) | 1 | 2015 |
| plant | Cercidiphyllum japonicum | a flowering plant | 3 | 2000 |
| plant | Cercis siliquastrum | Judas Tree | 16 | 2019 |
| plant | Cerinthe major | a flowering plant | 7 | 2020 |
| plant | Ceterach officinarum | Rustyback | 1099 | 2020 |
| plant | Chaenomeles japonica | a flowering plant | 1 | 2018 |
| plant | Chaenomeles speciosa | Japanese Quince | 2 | 2002 |
| plant | Chaenorhinum minus | Small Toadflax | 242 | 2018 |
| plant | Chaenorhinum origanifolium | Malling Toadflax | 2 | 2012 |
| plant | Chaenostoma cordatum | Bacopa | 2 | 2016 |
| plant | Chaerophyllum temulum | Rough Chervil | 1364 | 2019 |
| plant | Chamaecyparis | a Chamaecyparis species (unidentified) | 4 | 2009 |
| plant | Chamaecyparis lawsoniana | Lawson's Cypress | 201 | 2020 |
| plant | Chamaecyparis lawsoniana 'Erecta Viridis' | a conifer | 1 | 2015 |
| plant | Chamaecyparis pisifera | Sawara Cypress | 14 | 2013 |
| plant | Chamaemelum nobile | Chamomile | 12 | 2017 |
| plant | Chamerion angustifolium | Rosebay Willowherb | 2721 | 2022 |
| plant | Chelidonium majus | Greater Celandine | 512 | 2020 |
| plant | Chenopodium | a goosefoot (unidentified) | 11 | 2017 |
| plant | Chenopodium album | Fat-hen | 517 | 2020 |
| plant | Chenopodium album agg. | Fat-hen (agg.) | 999 | 2011 |
| plant | Chenopodium album var. lanceolatum | a goosefoot | 1 | 1927 |
| plant | Chenopodium ambrosioides | Mexican Tea | 4 | 1930 |
| plant | Chenopodium berlandieri | Pitseed Goosefoot | 5 | 1928 |
| plant | Chenopodium bonus-henricus | Good King Henry | 90 | 2017 |
| plant | Chenopodium borbasioides | a flowering plant | 2 | 1957 |
| plant | Chenopodium botrys | a flowering plant | 1 | 1939 |
| plant | Chenopodium chenopodioides | Saltmarsh Goosefoot | 1 | 2000 |
| plant | Chenopodium desiccatum | Slimleaf Goosefoot | 5 | 1957 |
| plant | Chenopodium diversifolium | a goosefoot | 1 | 1933 |
| plant | Chenopodium ficifolium | Fig-leaved Goosefoot | 150 | 2016 |
| plant | Chenopodium giganteum | Tree Spinnach | 5 | 2018 |
| plant | Chenopodium glaucum | Oak-leaved Goosefoot | 7 | 1998 |
| plant | Chenopodium hircinum | Foetid Goosefoot | 10 | 1934 |
| plant | Chenopodium hybridum | Maple-leaved Goosefoot | 1 | 1938 |
| plant | Chenopodium missouriense | a flowering plant | 4 | 1957 |
| plant | Chenopodium murale | Nettle-leaved Goosefoot | 13 | 2006 |
| plant | Chenopodium opulifolium | Grey Goosefoot | 7 | 1938 |
| plant | Chenopodium polyspermum | Many-seeded Goosefoot | 260 | 2020 |
| plant | Chenopodium probstii | Probst's Goosefoot | 2 | 1997 |
| plant | Chenopodium rubrum | Red Goosefoot | 335 | 2018 |
| plant | Chenopodium strictum | Striped Goosefoot | 2 | 1930 |
| plant | Chenopodium x variabile | a goosefoot | 1 | 1935 |
| plant | Chimonanthus praecox | Wintersweet | 1 | 1984 |
| plant | Chloris virgata | Feathery Rhodes-grass | 1 | 1959 |
| plant | Choisya ternata | Mexican Orange | 10 | 2019 |
| plant | Chorispora tenella | a flowering plant | 2 | 1931 |
| plant | Chrysosplenium alternifolium | Alternate-leaved Golden-saxifrage | 18 | 2017 |
| plant | Chrysosplenium oppositifolium | Opposite-leaved Golden-saxifrage | 531 | 2021 |
| plant | Cicer arietinum | Chick Pea | 1 | 1924 |
| plant | Cicerbita macrophylla | Common Blue-sow-thistle | 12 | 2018 |
| plant | Cicerbita macrophylla subsp. uralensis | a common blue-sow-thistle | 11 | 1999 |
| plant | Cichorium intybus | Chicory | 175 | 2019 |
| plant | Circaea lutetiana | Enchanter's-nightshade | 2433 | 2021 |
| plant | Cirsium | a Cirsium thistle (unidentified) | 30 | 2022 |
| plant | Cirsium acaule | Dwarf Thistle | 1211 | 2020 |
| plant | Cirsium arvense | Creeping Thistle | 7362 | 2021 |
| plant | Cirsium arvense var. incanum | a creeping thistle | 4 | 2021 |
| plant | Cirsium dissectum | Meadow Thistle | 141 | 2019 |
| plant | Cirsium dissectum x palustre = C. x forsteri | a thistle | 2 | 1998 |
| plant | Cirsium eriophorum | Woolly Thistle | 1157 | 2021 |
| plant | Cirsium heterophyllum | Melancholy Thistle | 1 | 1994 |
| plant | Cirsium oleraceum | Cabbage Thistle | 2 | 1982 |
| plant | Cirsium palustre | Marsh Thistle | 2184 | 2020 |
| plant | Cirsium sp. or Carlina sp. or Onopordum sp. or Silybum sp. or Carduus sp. (unidentified thistle) | a thistle (unidentified) | 148 | 2020 |
| plant | Cirsium tuberosum | Tuberous Thistle | 1 | 1996 |
| plant | Cirsium vulgare | Spear Thistle | 5956 | 2022 |
| plant | Cirsium vulgare x acaule = C. x sabaudum | a thistle | 1 | 2004 |
| plant | Cistus | a Cistus species (unidentified) | 2 | 2015 |
| plant | Citrullus lanatus | Water Melon | 3 | 1996 |
| plant | Cladium mariscus | Great Fen-sedge | 1 | 1921 |
| plant | Clarkia amoena | Godetia | 1 | 1985 |
| plant | Claytonia perfoliata | Spring Beauty | 12 | 2019 |
| plant | Claytonia sibirica | Pink Purslane | 2 | 2019 |
| plant | Clematis | a clematis (unidentified) | 28 | 2022 |
| plant | Clematis armandii | a clematis | 2 | 2013 |
| plant | Clematis flammula | Virgin's-bower | 2 | 1936 |
| plant | Clematis montana | Himalayan Clematis | 6 | 2019 |
| plant | Clematis tangutica | Orange-peel Clematis | 2 | 2010 |
| plant | Clematis vitalba | Traveller's Joy | 4619 | 2021 |
| plant | Clematis viticella | Purple Clematis | 1 | 1999 |
| plant | Clerodendrum | a Clerodendrum species (unidentified) | 9 | 2011 |
| plant | Clinopodium | a calamint (unidentified) | 9 | 2017 |
| plant | Clinopodium acinos | Basil Thyme | 73 | 2019 |
| plant | Clinopodium ascendens | Common Calamint | 287 | 2020 |
| plant | Clinopodium menthifolium | Wood Calamint | 10 | 2002 |
| plant | Clinopodium vulgare | Wild Basil | 766 | 2021 |
| plant | Cochlearia anglica | English Scurvygrass | 275 | 2019 |
| plant | Cochlearia danica | Danish Scurvygrass | 892 | 2020 |
| plant | Cochlearia officinalis | Common Scurvygrass | 99 | 2017 |
| plant | Cochlearia officinalis (sens.lat.) | Common Scurvygrass sens.lat. | 7 | 2002 |
| plant | Coeloglossum viride | Frog Orchid | 1 | 1988 |
| plant | Coincya monensis subsp. cheiranthos | Wallflower Cabbage | 4 | 2003 |
| plant | Colchicum autumnale | Meadow Saffron | 124 | 2020 |
| plant | Collomia linearis | a flowering plant | 2 | 1924 |
| plant | Colutea | a Colutea species (unidentified) | 1 | 2013 |
| plant | Colutea arborescens | Bladder-senna | 10 | 2010 |
| plant | Commelina communis | a flowering plant | 1 | 1931 |
| plant | Coniferophyta | a conifer (unidentified) | 72 | 2021 |
| plant | Conium maculatum | Hemlock | 1456 | 2022 |
| plant | Conopodium | a Conopodium species (unidentified) | 1 | 2001 |
| plant | Conopodium majus | Pignut | 1647 | 2020 |
| plant | Conringia orientalis | Hare's-ear Mustard | 6 | 1954 |
| plant | Consolida ajacis | Larkspur | 5 | 1987 |
| plant | Consolida regalis | Forking Larkspur | 2 | 1939 |
| plant | Convallaria majalis | Lily of the Valley | 28 | 2019 |
| plant | Convolvulus | a convolvulus bindweed (unidentified) | 74 | 2019 |
| plant | Convolvulus arvensis | Field Bindweed | 3675 | 2021 |
| plant | Convolvulus arvensis var. stonestreetii | a field bindweed | 1 | 2021 |
| plant | Convolvulus stachydifolius | a flowering plant | 1 | 1937 |
| plant | Conyza | a Conyza species (unidentified) | 1 | 2019 |
| plant | Conyza bonariensis | Argentine Fleabane | 13 | 2020 |
| plant | Conyza canadensis | Canadian Fleabane | 429 | 2022 |
| plant | Conyza floribunda | Bilbao Fleabane | 11 | 2020 |
| plant | Conyza sumatrensis | Guernsey Fleabane | 92 | 2019 |
| plant | Corchorus olitorius | Tossa Jute | 1 | 1932 |
| plant | Cordyline | a Cordyline species (unidentified) | 1 | 2019 |
| plant | Cordyline australis | Cabbage-palm | 94 | 2017 |
| plant | Coriandrum sativum | Coriander | 6 | 2009 |
| plant | Cornus | a dogwood (unidentified) | 116 | 2015 |
| plant | Cornus alba | White Dogwood | 29 | 2019 |
| plant | Cornus capitata | Bentham's Dogwood | 1 | 2006 |
| plant | Cornus controversa variegata | Table Dogwood | 1 | 2015 |
| plant | Cornus mas | Cornelian-cherry | 15 | 2007 |
| plant | Cornus sanguinea | Dogwood | 5538 | 2022 |
| plant | Cornus sericea | Red-osier Dogwood | 7 | 2016 |
| plant | Coronilla scorpioides | Annual Scorpion-vetch | 2 | 1930 |
| plant | Cortaderia | a Cortaderia species (unidentified) | 2 | 2009 |
| plant | Cortaderia selloana | Pampas Grass | 28 | 2019 |
| plant | Corydalis | a corydalis (unidentified) | 3 | 2013 |
| plant | Corydalis cheilanthifolia | Fern-leaved Corydalis | 3 | 2009 |
| plant | Corydalis solida | Bird-in-a-bush | 1 | 2010 |
| plant | Corylus | a Corylus species (unidentified) | 22 | 2021 |
| plant | Corylus avellana | Hazel | 10319 | 2022 |
| plant | Corylus colurna | Turkish Hazel | 15 | 2016 |
| plant | Corylus maxima | Filbert | 1 | 2012 |
| plant | Cosmos bipinnatus | Mexican Aster | 3 | 2008 |
| plant | Cotinus coggygria | Smoke-tree | 57 | 2019 |
| plant | Cotoneaster | a cotoneaster (unidentified) | 252 | 2021 |
| plant | Cotoneaster bullatus | Hollyberry Cotoneaster | 12 | 2015 |
| plant | Cotoneaster cambricus | a Cotoneaster | 1 | 2012 |
| plant | Cotoneaster dielsianus | Diel's Cotoneaster | 3 | 1995 |
| plant | Cotoneaster divaricatus | Spreading Cotoneaster | 3 | 2019 |
| plant | Cotoneaster franchetii | Franchet's Cotoneaster | 20 | 2016 |
| plant | Cotoneaster frigidus | Tree Cotoneaster | 25 | 2016 |
| plant | Cotoneaster frigidus x salicifolius = C. x watereri | Waterer's Cotoneaster | 62 | 2014 |
| plant | Cotoneaster hjelmqvistii | Hjelmqvist's Cotoneaster | 1 | 1998 |
| plant | Cotoneaster horizontalis | Wall Cotoneaster | 309 | 2020 |
| plant | Cotoneaster horizontalis agg. | a Wall Cotoneaster (agg.) | 46 | 2011 |
| plant | Cotoneaster integrifolius | Entire-Leaved Cotoneaster | 56 | 2006 |
| plant | Cotoneaster lacteus | Late Cotoneaster | 8 | 2014 |
| plant | Cotoneaster microphyllus | a cotoneaster | 2 | 1997 |
| plant | Cotoneaster microphyllus agg. | Small-Leaved Cotoneaster | 8 | 2003 |
| plant | Cotoneaster prostratus | a cotoneaster | 2 | 2014 |
| plant | Cotoneaster rehderi | Bullate Cotoneaster | 3 | 2006 |
| plant | Cotoneaster rotundifolius | a cotoneaster | 4 | 2009 |
| plant | Cotoneaster salicifolius | Willow-leaved Cotoneaster | 5 | 2013 |
| plant | Cotoneaster salicifolius x dammeri = C. 'Hybridus Pendulus' | Weeping Cotoneaster | 1 | 2014 |
| plant | Cotoneaster simonsii | Himalayan Cotoneaster | 124 | 2019 |
| plant | Cotoneaster sternianus | Stern's Cotoneaster | 9 | 2016 |
| plant | Cotoneaster vilmorinianus | a cotoneaster | 3 | 1995 |
| plant | Cotula coronopifolia | Buttonweed | 2 | 1990 |
| plant | Crambe maritima | Sea-kale | 1 | 2002 |
| plant | Crassula helmsii | New Zealand Pigmyweed | 33 | 2017 |
| plant | Crataegus | a Crataegus species (unidentified) | 15 | 2016 |
| plant | Crataegus crus-galli | Cockspur-thorn | 2 | 2002 |
| plant | Crataegus laevigata | Midland Hawthorn | 40 | 2021 |
| plant | Crataegus monogyna | Hawthorn | 16157 | 2022 |
| plant | Crataegus monogyna x laevigata = C. x media | Hybrid Hawthorn | 19 | 2016 |
| plant | Crataegus orientalis | Oriental Hawthorn | 1 | 2000 |
| plant | Crataegus persimilis | Broad-leaved Cockspur-thorn | 8 | 2014 |
| plant | Crataegus x lavallei | Hybrid Cockspur-thorn | 37 | 2016 |
| plant | Crepis | a hawk's-beard (unidentified) | 20 | 2022 |
| plant | Crepis biennis | Rough Hawk's-beard | 155 | 2019 |
| plant | Crepis capillaris | Smooth Hawk's-beard | 2344 | 2020 |
| plant | Crepis capillaris var. agrestis | a flowering plant | 1 | 2012 |
| plant | Crepis foetida | Stinking Hawk's-beard | 1 | 1939 |
| plant | Crepis setosa | Bristly Hawk's-beard | 4 | 2001 |
| plant | Crepis vesicaria | Beaked Hawk's-beard | 1814 | 2021 |
| plant | Crepis vesicaria subsp. taraxacifolia | a flowering plant | 5 | 2006 |
| plant | Crithmum maritimum | Rock Samphire | 156 | 2019 |
| plant | Crithopsis delileana | a flowering plant | 1 | 1937 |
| plant | Crocosmia | a Crocosmia species (unidentified) | 2 | 2021 |
| plant | Crocosmia paniculata | Aunt-Eliza | 1 | 2015 |
| plant | Crocosmia pottsii | Pott's Monbretia | 2 | 2009 |
| plant | Crocosmia pottsii x aurea = C. x crocosmiiflora | Montbretia | 155 | 2020 |
| plant | Crocus | a crocus (unidentified) | 9 | 2020 |
| plant | Crocus angustifolius x flavus = C. x stellaris | a flowering plant | 4 | 2013 |
| plant | Crocus flavus | Yellow Crocus | 7 | 2000 |
| plant | Crocus nudiflorus | Autumn Crocus | 18 | 2021 |
| plant | Crocus tommasinianus | Early Crocus | 22 | 2018 |
| plant | Crocus vernus | Spring Crocus | 19 | 2017 |
| plant | Crocus vernus subsp. vernus | a flowering plant | 3 | 2013 |
| plant | Cruciata laevipes | Crosswort | 131 | 2021 |
| plant | Cryptomeria japonica | Japanese Red-cedar | 21 | 2015 |
| plant | Cucumis melo | Melon | 3 | 1996 |
| plant | Cucumis sativus | Cucumber | 3 | 2013 |
| plant | Cucurbita maxima | Pumpkin | 2 | 2020 |
| plant | Cucurbita pepo | Marrow | 6 | 2013 |
| plant | Cuminum cyminum | Cumin | 1 | 1937 |
| plant | Cupressaceae | a cypress (unidentified) | 21 | 2019 |
| plant | Cupressus | a Cupressus species (unidentified) | 31 | 2019 |
| plant | Cupressus macrocarpa | Monterey Cypress | 71 | 2015 |
| plant | Cupressus macrocarpa x Xanthocyparis nootkatensis = X Cuprocyparis leylandii | Leyland Cypress | 168 | 2021 |
| plant | Cupressus sempervirens | Italian Cypress | 18 | 2015 |
| plant | Cuscuta | a Cuscuta species (unidentified) | 1 | 2011 |
| plant | Cuscuta campestris | Yellow Dodder | 2 | 1999 |
| plant | Cuscuta epithymum | Dodder | 20 | 2011 |
| plant | Cuscuta europaea | Greater Dodder | 157 | 2018 |
| plant | Cyclamen | a cyclamen (unidentified) | 10 | 2016 |
| plant | Cyclamen hederifolium | Cyclamen | 94 | 2020 |
| plant | Cyclamen persicum | a flowering plant | 2 | 2009 |
| plant | Cyclamen repandum | Spring Sowbread | 6 | 2018 |
| plant | Cyclospermum leptophyllum | a flowering plant | 2 | 1961 |
| plant | Cydonia oblonga | Quince | 12 | 2017 |
| plant | Cymbalaria muralis | Ivy-leaved Toadflax | 2625 | 2021 |
| plant | Cymbalaria muralis subsp. muralis | an ivy-leaved toadflax | 12 | 2014 |
| plant | Cymbalaria pallida | Italian Toadflax | 1 | 2016 |
| plant | Cynara cardunculus | Globe Artichoke | 14 | 2020 |
| plant | Cynodon dactylon | Bermuda-grass | 31 | 2011 |
| plant | Cynoglossum officinale | Hound's-tongue | 150 | 2019 |
| plant | Cynosurus cristatus | Crested Dog's-tail | 4384 | 2022 |
| plant | Cynosurus echinatus | Rough Dog's-tail | 1 | 1916 |
| plant | Cyperaceae | a Cyperaceae species (unidentified) | 1 | 2008 |
| plant | Cyperus eragrostis | Pale Galingale | 7 | 2018 |
| plant | Cyperus fuscus | Brown Galingale | 57 | 2015 |
| plant | Cyperus involucratus | a flowering plant | 1 | 2016 |
| plant | Cyperus longus | Galingale | 45 | 2016 |
| plant | Cyrtomium | a Cyrtomium species (unidentified) | 1 | 2009 |
| plant | Cyrtomium falcatum | House Holly-fern | 3 | 2014 |
| plant | Cyrtomium fortunei | Fortune's Holly-fern | 1 | 2009 |
| plant | Cystopteris fragilis | Brittle Bladder-fern | 66 | 2021 |
| plant | Cytisus | a Cytisus species (unidentified) | 1 | 2016 |
| plant | Cytisus battandieri | Pineapple Broom | 1 | 2013 |
| plant | Cytisus multiflorus x purgans (C. x praecox) | Allgold Broom | 1 | 2018 |
| plant | Cytisus scoparius | Broom | 157 | 2021 |
| plant | Cytisus scoparius subsp. scoparius | a broom | 144 | 2013 |
| reptile | Colubridae sp. or Viperidae sp. (unidentified) | a snake (unidentified) | 10 | 2016 |
| sea-fan, sea anemone or jellyfish | Clava multicornis | a Sea-fan/Sea Anemone/Jellyfish | 4 | 1976 |
| sea-fan, sea anemone or jellyfish | Clytia hemisphaerica | a Sea-fan/Sea Anemone/Jellyfish | 1 | 1939 |
| slime mould | Calomyxa metallica | a slime mould | 4 | 2008 |
| slime mould | Ceratiomyxa | a Ceratiomyxa slime mould (unidentified) | 1 | 2012 |
| slime mould | Ceratiomyxa fruticulosa | a slime mould | 18 | 2017 |
| slime mould | Ceratiomyxa fruticulosa var. fruticulosa | a slime mould | 30 | 2013 |
| slime mould | Comatricha nigra | a slime mould | 5 | 2008 |
| slime mould | Craterium leucocephalum var. leucocephalum | a slime mould | 1 | 2015 |
| slime mould | Craterium minutum | a slime mould | 5 | 2014 |
| slime mould | Cribraria argillacea | a slime mould | 4 | 2017 |
| slime mould | Cribraria aurantiaca | a slime mould | 1 | 2008 |
| slime mould | Cribraria cancellata | a slime mould | 1 | 2016 |
| slime mould | Cribraria cancellata var. cancellata | a slime mould | 1 | 2008 |
| slime mould | Cribraria minutissima | a slime mould | 1 | 2016 |
| spider | Centromerita bicolor | a money spider | 17 | 2019 |
| spider | Centromerus cavernarum | a money spider | 1 | 2002 |
| spider | Centromerus dilutus | a money spider | 8 | 1998 |
| spider | Centromerus sylvaticus | a money spider | 2 | 2019 |
| spider | Ceratinella brevipes | a money spider | 2 | 2003 |
| spider | Cheiracanthium erraticum | a foliage spider | 7 | 2016 |
| spider | Cheiracanthium virescens | a foliage spider | 2 | 1989 |
| spider | Cicurina cicur | a cobweb spider | 4 | 1990 |
| spider | Clubiona | a foliage spider (unidentified) | 8 | 2019 |
| spider | Clubiona brevipes | a foliage spider | 15 | 2014 |
| spider | Clubiona comta | a foliage spider | 19 | 2013 |
| spider | Clubiona corticalis | a foliage spider | 7 | 2009 |
| spider | Clubiona diversa | a foliage spider | 2 | 1985 |
| spider | Clubiona lutescens | a foliage spider | 7 | 1999 |
| spider | Clubiona neglecta (sensu lato) | a foliage spider | 2 | 1989 |
| spider | Clubiona pallidula | a foliage spider | 2 | 1989 |
| spider | Clubiona phragmitis | a foliage spider | 11 | 1999 |
| spider | Clubiona reclusa | a foliage spider | 14 | 2013 |
| spider | Clubiona stagnatilis | a foliage spider | 4 | 1998 |
| spider | Clubiona subtilis | a foliage spider | 2 | 2003 |
| spider | Clubiona terrestris | a foliage spider | 24 | 2013 |
| spider | Cnephalocotes obscurus | a money spider | 4 | 2019 |
| spider | Coelotes atropos | a cobweb spider | 24 | 2019 |
| spider | Coelotes terrestris | a cobweb spider | 2 | 1999 |
| spider | Collinsia inerrans | a money spider | 12 | 2003 |
| spider | Cozyptila blackwalli | a crab spider | 1 | 1968 |
| spider | Crustulina guttata | a comb-footed spider | 2 | 1988 |
| spider | Cyclosa conica | Trash-line Spider | 16 | 2020 |
| springtail | Ceratophysella armata | a springtail (Collembola) | 2 | 1925 |
| springtail | Collembola | a springtail (unidentified) | 32 | 2018 |
| springtail | Cyphoderus albinus | a springtail (Collembola) | 1 | 2015 |
| tick or mite (acarine) | Camisia | a Camisia species (unidentified) | 1 | 1983 |
| tick or mite (acarine) | Cecidophyes galii | a gall mite | 5 | 2012 |
| tick or mite (acarine) | Cecidophyes nudus | Galium Gall Mite | 1 | 2020 |
| tick or mite (acarine) | Cecidophyes rouhollahi | Galium Gall Mite | 1 | 2018 |
| tick or mite (acarine) | Cecidophyopsis ribis | a gall mite | 1 | 2002 |
| true fly - | Calamoncosis aprica | a fly | 3 | 2009 |
| true fly - | Calamoncosis glyceriae | a fly | 3 | 1999 |
| true fly - | Calamoncosis minima | a fly | 1 | 1983 |
| true fly - | Calliopum | a Calliopum species (unidentified) | 1 | 2015 |
| true fly - | Calliopum aeneum | a fly | 1 | 1993 |
| true fly - | Calliopum elisae | a fly | 3 | 2009 |
| true fly - | Calliopum simillimum | a fly | 9 | 2021 |
| true fly - | Calliopum tuberculosum | a fly | 12 | 2020 |
| true fly - | Calliphora | a Calliphora true fly (unidentified) | 9 | 2022 |
| true fly - | Calliphora vicina | a blue bottle or green bottle | 26 | 2020 |
| true fly - | Calliphora vomitoria | a blue bottle or green bottle | 15 | 2019 |
| true fly - | Calliphoridae | a blue bottle or green bottle or cluster fly (unidentified) | 26 | 2018 |
| true fly - | Callomyia dives | a big-footed fly | 1 | 1900 |
| true fly - | Calycomyza humeralis | a leaf-mining fly | 1 | 2014 |
| true fly - | Camilla glabra | a fly | 2 | 2001 |
| true fly - | Campichoeta obscuripennis | a fly | 2 | 2009 |
| true fly - | Campichoeta punctum | a fly | 1 | 1999 |
| true fly - | Canace nasica | a fly | 1 | 1995 |
| true fly - | Carcelia lucorum | a parasitic fly | 2 | 2000 |
| true fly - | Cecidomyiidae | a Cecidomyiidae species (unidentified) | 4 | 2008 |
| true fly - | Cephalops pannonicus | a big-headed fly | 2 | 2008 |
| true fly - | Cephalops ultimus | a big-headed fly | 1 | 1999 |
| true fly - | Cephalops varipes | a big-headed fly | 6 | 2003 |
| true fly - | Ceratinostoma ostiorum | a dung fly | 1 | 2019 |
| true fly - | Cerodontha atra | a leaf-mining fly | 4 | 2006 |
| true fly - | Cerodontha bimaculata | a leaf-mining fly | 4 | 2006 |
| true fly - | Cerodontha biseta | a leaf-mining fly | 3 | 2008 |
| true fly - | Cerodontha capitata | a leaf-mining fly | 4 | 2002 |
| true fly - | Cerodontha denticornis | a leaf-mining fly | 16 | 2008 |
| true fly - | Cerodontha iraeos | a leaf-mining fly | 2 | 2020 |
| true fly - | Cerodontha lateralis | a leaf-mining fly | 3 | 2008 |
| true fly - | Cerodontha luctuosa | a leaf-mining fly | 3 | 2001 |
| true fly - | Ceroxys urticae | a fly | 3 | 2019 |
| true fly - | Cetema elongatum | a fly | 1 | 2002 |
| true fly - | Cetema neglectum | a fly | 15 | 2009 |
| true fly - | Cetema simile | a fly | 3 | 2004 |
| true fly - | Chalarus fimbriatus | a big-headed fly | 1 | 1999 |
| true fly - | Chalarus latifrons | a big-headed fly | 1 | 2000 |
| true fly - | Chalarus spurius | a big-headed fly | 3 | 2003 |
| true fly - | Chamaemyia aridella | a fly | 6 | 2013 |
| true fly - | Chamaemyia fasciata | a fly | 1 | 2001 |
| true fly - | Chamaemyia herbarum | a fly | 1 | 2008 |
| true fly - | Chamaemyia nigripalpis | a fly | 1 | 2000 |
| true fly - | Chamaemyia polystigma | a fly | 11 | 2006 |
| true fly - | Chamaepsila bicolor | a fly | 1 | 2006 |
| true fly - | Chamaepsila persimilis | a fly | 1 | 2008 |
| true fly - | Chaoborus | a Chaoborus species (unidentified) | 5 | 2007 |
| true fly - | Chironominae | a Chironominae species (unidentified) | 4 | 1991 |
| true fly - | Chirosia betuleti | a fly | 9 | 2003 |
| true fly - | Chirosia grossicauda | a fly | 8 | 2016 |
| true fly - | Chirosia histricina | a fly | 1 | 2011 |
| true fly - | Chloromyia | a Chloromyia species (unidentified) | 1 | 2019 |
| true fly - | Chloropidae | a Chloropidae species (unidentified) | 3 | 2020 |
| true fly - | Chlorops calceatus | a fly | 4 | 2002 |
| true fly - | Chlorops hypostigma | a fly | 6 | 2008 |
| true fly - | Chlorops interruptus | a fly | 1 | 2017 |
| true fly - | Chlorops laetus | a fly | 1 | 1950 |
| true fly - | Chlorops limbatus | a fly | 2 | 1983 |
| true fly - | Chlorops obscurellus | a fly | 2 | 1983 |
| true fly - | Chlorops pumilionis | a fly | 13 | 2008 |
| true fly - | Chlorops rufinus | a fly | 5 | 2006 |
| true fly - | Chlorops scalaris | a fly | 3 | 2006 |
| true fly - | Chlorops serenus | a fly | 3 | 2008 |
| true fly - | Chlorops speciosus | a fly | 5 | 2004 |
| true fly - | Choerades marginatus | Golden-haired Robberfly | 2 | 2001 |
| true fly - | Chonocephalus | a Chonocephalus species (unidentified) | 2 | 1997 |
| true fly - | Chromatomyia | a Chromatomyia species (unidentified) | 4 | 2013 |
| true fly - | Chromatomyia aprilina | a leaf-mining fly | 1 | 2020 |
| true fly - | Chromatomyia centaurii | a leaf-mining fly | 1 | 2006 |
| true fly - | Chromatomyia horticola | a leaf-mining fly | 3 | 2014 |
| true fly - | Chromatomyia lonicerae | a leaf-mining fly | 2 | 2014 |
| true fly - | Chromatomyia milii | a leaf-mining fly | 10 | 2020 |
| true fly - | Chromatomyia nigra | a leaf-mining fly | 23 | 2020 |
| true fly - | Chromatomyia periclymeni | a leaf-mining fly | 1 | 2020 |
| true fly - | Chromatomyia primulae | a leaf-mining fly | 6 | 2021 |
| true fly - | Chromatomyia ramosa | a leaf-mining fly | 3 | 2020 |
| true fly - | Chromatomyia scolopendri | a leaf-mining fly | 11 | 2020 |
| true fly - | Chromatomyia syngenesiae | a leaf-mining fly | 5 | 2017 |
| true fly - | Chrysotoxum | a Chrysotoxum species (unidentified) | 5 | 2021 |
| true fly - | Chrysotus | a Chrysotus species (unidentified) | 1 | 2011 |
| true fly - | Chyliza extenuata | a fly | 3 | 2022 |
| true fly - | Chyliza leptogaster | a fly | 3 | 2004 |
| true fly - | Chyromyidae | a Chyromyidae species (unidentified) | 1 | 2016 |
| true fly - | Cinochira atra | a parasitic fly | 1 | 2004 |
| true fly - | Cistogaster globosa | a parasitic fly | 3 | 2020 |
| true fly - | Cleigastra apicalis | a dung fly | 2 | 2004 |
| true fly - | Clinohelea | a Clinohelea species (unidentified) | 2 | 1983 |
| true fly - | Clusia flava | a fly | 6 | 2001 |
| true fly - | Clusia tigrina | a fly | 11 | 2020 |
| true fly - | Clusiodes albimanus | a fly | 12 | 2009 |
| true fly - | Clusiodes gentilis | a fly | 2 | 2006 |
| true fly - | Clusiodes verticalis | a fly | 3 | 2000 |
| true fly - | Cnemacantha muscaria | a fly | 8 | 2008 |
| true fly - | Coboldia fuscipes | a fly | 1 | 1996 |
| true fly - | Coelopa frigida | a wrack fly | 2 | 2002 |
| true fly - | Coenia curvicauda | a shore fly | 1 | 2009 |
| true fly - | Coenia palustris | a shore fly | 1 | 2009 |
| true fly - | Coenosia agromyzina | a muscid fly | 5 | 2009 |
| true fly - | Coenosia albicornis | a muscid fly | 2 | 2001 |
| true fly - | Coenosia atra | a muscid fly | 2 | 2002 |
| true fly - | Coenosia femoralis | a muscid fly | 2 | 2013 |
| true fly - | Coenosia humilis | a muscid fly | 1 | 1998 |
| true fly - | Coenosia infantula | a muscid fly | 18 | 2008 |
| true fly - | Coenosia mollicula | a muscid fly | 8 | 2009 |
| true fly - | Coenosia pedella | a muscid fly | 2 | 2013 |
| true fly - | Coenosia pumila | a muscid fly | 5 | 2013 |
| true fly - | Coenosia testacea | a muscid fly | 14 | 2015 |
| true fly - | Coenosia tigrina | a muscid fly | 11 | 2020 |
| true fly - | Conicera dauci | a scuttle fly | 3 | 2008 |
| true fly - | Conioscinella frontella | a fly | 3 | 2004 |
| true fly - | Conioscinella gallarum | a fly | 1 | 2006 |
| true fly - | Coproica ferruginata | a lesser dung fly | 1 | 2020 |
| true fly - | Coproica pusio | a lesser dung fly | 1 | 2003 |
| true fly - | Copromyza equina | a lesser dung fly | 1 | 1995 |
| true fly - | Copromyza nigrina | a lesser dung fly | 1 | 1994 |
| true fly - | Cordilura albipes | a dung fly | 9 | 2021 |
| true fly - | Cordilura ciliata | a dung fly | 1 | 1999 |
| true fly - | Cordilura pubera | a dung fly | 4 | 2004 |
| true fly - | Cordilura pudica | a dung fly | 1 | 2006 |
| true fly - | Coremacera | a Coremacera species (unidentified) | 1 | 2014 |
| true fly - | Coremacera marginata | a snail-killing fly | 30 | 2021 |
| true fly - | Corynoneura | a Corynoneura species (unidentified) | 1 | 1983 |
| true fly - | Corynoptera flavicauda | a fly | 1 | 2001 |
| true fly - | Corynoptera forcipata | a fly | 2 | 2021 |
| true fly - | Crumomyia fimetaria | a lesser dung fly | 2 | 2020 |
| true fly - | Crumomyia nitida | a lesser dung fly | 4 | 2020 |
| true fly - | Crumomyia pedestris | a lesser dung fly | 1 | 2021 |
| true fly - | Crumomyia roserii | a lesser dung fly | 3 | 2020 |
| true fly - | Cryptonevra diadema | a fly | 1 | 2009 |
| true fly - | Cryptonevra flavitarsis | a fly | 10 | 2009 |
| true fly - | Culicoides | a Culicoides species (unidentified) | 3 | 2014 |
| true fly - | Cynomya mortuorum | a blue bottle or green bottle | 5 | 1997 |
| true fly - | Cyzenis albicans | a parasitic fly | 1 | 2019 |
| true fly - cranefly | Cheilotrichia cinerascens | a cranefly | 5 | 2009 |
| true fly - cranefly | Crypteria limnophiloides | a cranefly | 2 | 2003 |
| true fly - cranefly | Ctenophora pectinicornis | a cranefly | 6 | 2018 |
| true fly - (diptera) | Campiglossa malaris | an insect - true fly (Diptera) | 5 | 2009 |
| true fly - (diptera) | Campiglossa plantaginis | an insect - true fly (Diptera) | 11 | 2019 |
| true fly - (diptera) | Cerodontha iridis | an insect - true fly (Diptera) | 1 | 2015 |
| true fly - (diptera) | Cerodontha morosa | an insect - true fly (Diptera) | 3 | 2006 |
| true fly - (diptera) | Cerodontha spinata | an insect - true fly (Diptera) | 1 | 2001 |
| true fly - (diptera) | Chamaepsila rosae (preocc.) | an insect - true fly (Diptera) | 7 | 2001 |
| true fly - (diptera) | Chironomus alpestris | an insect - true fly (Diptera) | 1 | 1983 |
| true fly - (diptera) | Coquillettidia richiardii | an insect - true fly (Diptera) | 7 | 2012 |
| true fly - (diptera) | Corynoptera inundata | an insect - true fly (Diptera) | 1 | 2003 |
| true fly - (diptera) | Crataerina hirundinis | an insect - true fly (Diptera) | 1 | 1969 |
| true fly - (diptera) | Cratyna vagabunda | an insect - true fly (Diptera) | 1 | 2006 |
| true fly - (diptera) | Crossopalpus nigritellus | an insect - true fly (Diptera) | 1 | 1983 |
| true fly - fly | Colobaea bifasciella | a snail-killing fly | 1 | 2009 |
| true fly - fly | Colobaea distincta | a snail-killing fly | 1 | 2009 |
| true fly - fly | Colobaea pectoralis | a snail-killing fly | 1 | 1984 |
| true fly - fly | Colobaea punctata | a snail-killing fly | 2 | 2004 |
| true fly - horse fly | Chrysops | a Chrysops horse fly (unidentified) | 1 | 2021 |
| true fly - horse fly | Chrysops caecutiens | a horse fly | 25 | 2017 |
| true fly - horse fly | Chrysops relictus | a horse fly | 14 | 2021 |
| true fly - horse fly | Chrysops viduatus | a horse fly | 10 | 2021 |
| true fly - hoverfly | Chalcosyrphus nemorum | a hoverfly | 7 | 2014 |
| true fly - hoverfly | Cheilosia | a Cheilosia hoverfly (unidentified) | 10 | 2017 |
| true fly - hoverfly | Cheilosia albipila | a hoverfly | 2 | 2000 |
| true fly - hoverfly | Cheilosia albitarsis | a hoverfly | 78 | 2021 |
| true fly - hoverfly | Cheilosia albitarsis (sens.lat.) | a hoverfly | 5 | 2018 |
| true fly - hoverfly | Cheilosia antiqua | a hoverfly | 4 | 2021 |
| true fly - hoverfly | Cheilosia barbata | a hoverfly | 3 | 1999 |
| true fly - hoverfly | Cheilosia bergenstammi | a hoverfly | 27 | 2020 |
| true fly - hoverfly | Cheilosia cynocephala | a hoverfly | 1 | 1970 |
| true fly - hoverfly | Cheilosia fraterna | a hoverfly | 11 | 2016 |
| true fly - hoverfly | Cheilosia griseiventris | a hoverfly | 1 | 2003 |
| true fly - hoverfly | Cheilosia grossa | a hoverfly | 13 | 2000 |
| true fly - hoverfly | Cheilosia illustrata | a hoverfly | 144 | 2020 |
| true fly - hoverfly | Cheilosia impressa | a hoverfly | 37 | 2020 |
| true fly - hoverfly | Cheilosia lasiopa | a hoverfly | 4 | 2011 |
| true fly - hoverfly | Cheilosia latifrons | a hoverfly | 9 | 2009 |
| true fly - hoverfly | Cheilosia longula | a hoverfly | 2 | 1999 |
| true fly - hoverfly | Cheilosia mutabilis | a hoverfly | 1 | 1950 |
| true fly - hoverfly | Cheilosia pagana | a hoverfly | 95 | 2020 |
| true fly - hoverfly | Cheilosia proxima | a hoverfly | 34 | 2020 |
| true fly - hoverfly | Cheilosia psilophthalma | a hoverfly | 1 | 2003 |
| true fly - hoverfly | Cheilosia ranunculi | a hoverfly | 10 | 2018 |
| true fly - hoverfly | Cheilosia scutellata | a hoverfly | 14 | 2021 |
| true fly - hoverfly | Cheilosia soror | a hoverfly | 33 | 2019 |
| true fly - hoverfly | Cheilosia urbana | a hoverfly | 3 | 2003 |
| true fly - hoverfly | Cheilosia variabilis | a hoverfly | 23 | 2018 |
| true fly - hoverfly | Cheilosia vernalis | a hoverfly | 26 | 2021 |
| true fly - hoverfly | Cheilosia vulpina | a hoverfly | 9 | 2020 |
| true fly - hoverfly | Chrysogaster | a Chrysogaster hoverfly (unidentified) | 3 | 2016 |
| true fly - hoverfly | Chrysogaster cemiteriorum | a hoverfly | 2 | 2000 |
| true fly - hoverfly | Chrysogaster solstitialis | a hoverfly | 26 | 2021 |
| true fly - hoverfly | Chrysotoxum bicinctum | a hoverfly | 182 | 2021 |
| true fly - hoverfly | Chrysotoxum cautum | a hoverfly | 55 | 2021 |
| true fly - hoverfly | Chrysotoxum elegans | a hoverfly | 15 | 2006 |
| true fly - hoverfly | Chrysotoxum festivum | a hoverfly | 28 | 2020 |
| true fly - hoverfly | Criorhina asilica | a hoverfly | 2 | 2008 |
| true fly - hoverfly | Criorhina berberina | a hoverfly | 15 | 2020 |
| true fly - hoverfly | Criorhina floccosa | a hoverfly | 11 | 2018 |
| true fly - hoverfly | Criorhina ranunculi | a hoverfly | 14 | 2015 |
| true fly - midge, gnat or mosquito | Camptocladius stercorarius | a non-biting midge | 1 | 1997 |
| true fly - midge, gnat or mosquito | Ceratopogonidae | a biting midge (unidentified) | 35 | 2016 |
| true fly - midge, gnat or mosquito | Cerotelion striatum | a fungus gnat | 1 | 2001 |
| true fly - midge, gnat or mosquito | Chaoboridae | a phantom midge (unidentified) | 33 | 2016 |
| true fly - midge, gnat or mosquito | Chaoboridae sp. or Dixidae sp. or Chaobridae sp. or Ceratopogonidae sp. or Thaumaleidae sp. or Cecidomyiidae sp. | a midge (unidentified) | 15 | 2011 |
| true fly - midge, gnat or mosquito | Chaoborus crystallinus | a phantom midge | 4 | 2009 |
| true fly - midge, gnat or mosquito | Chaoborus flavicans | a phantom midge | 1 | 1997 |
| true fly - midge, gnat or mosquito | Chaoborus pallidus | a phantom midge | 2 | 1997 |
| true fly - midge, gnat or mosquito | Chironomidae | a non-biting midge (unidentified) | 175 | 2018 |
| true fly - midge, gnat or mosquito | Chironomus | a Chironomus non-biting midge (unidentified) | 2 | 2010 |
| true fly - midge, gnat or mosquito | Chironomus cingulatus | a non-biting midge | 2 | 1996 |
| true fly - midge, gnat or mosquito | Chironomus longistylus | a non-biting midge | 2 | 2003 |
| true fly - midge, gnat or mosquito | Chironomus luridus | a non-biting midge | 3 | 2018 |
| true fly - midge, gnat or mosquito | Chironomus plumosus | a non-biting midge | 3 | 2019 |
| true fly - midge, gnat or mosquito | Chironomus pseudothummi | a non-biting midge | 1 | 1983 |
| true fly - midge, gnat or mosquito | Chironomus riparius | a non-biting midge | 1 | 1983 |
| true fly - midge, gnat or mosquito | Coelophthinia thoracica | a fungus gnat | 1 | 2000 |
| true fly - midge, gnat or mosquito | Coelosia flava | a fungus gnat | 1 | 2004 |
| true fly - midge, gnat or mosquito | Contarinia coryli | a gall midge | 1 | 2020 |
| true fly - midge, gnat or mosquito | Contarinia jacobaeae | a gall midge | 3 | 2000 |
| true fly - midge, gnat or mosquito | Contarinia tiliarum | a gall midge | 2 | 1997 |
| true fly - midge, gnat or mosquito | Cordyla brevicornis | a fungus gnat | 1 | 2020 |
| true fly - midge, gnat or mosquito | Cordyla crassicornis | a fungus gnat | 5 | 2003 |
| true fly - midge, gnat or mosquito | Cordyla fissa | a fungus gnat | 2 | 2001 |
| true fly - midge, gnat or mosquito | Cordyla murina | a fungus gnat | 1 | 2001 |
| true fly - midge, gnat or mosquito | Craneiobia corni | a gall midge | 1 | 2011 |
| true fly - midge, gnat or mosquito | Cricotopus sylvestris | a non-biting midge | 1 | 1983 |
| true fly - midge, gnat or mosquito | Culex | a Culex mosquito (unidentified) | 2 | 2013 |
| true fly - midge, gnat or mosquito | Culex pipiens | a mosquito | 31 | 2018 |
| true fly - midge, gnat or mosquito | Culex territans | a mosquito | 2 | 2007 |
| true fly - midge, gnat or mosquito | Culicidae | a Culicidae mosquito (unidentified) | 82 | 2018 |
| true fly - midge, gnat or mosquito | Culicoides achrayi | a biting midge | 1 | 2009 |
| true fly - midge, gnat or mosquito | Culicoides dewulfi | a biting midge | 1 | 2009 |
| true fly - midge, gnat or mosquito | Culicoides obsoletus | a biting midge | 2 | 2009 |
| true fly - midge, gnat or mosquito | Culicoides pulicaris | a biting midge | 3 | 2009 |
| true fly - midge, gnat or mosquito | Culicoides punctatus | a biting midge | 1 | 2009 |
| true fly - midge, gnat or mosquito | Culicoides scoticus | a biting midge | 1 | 2009 |
| true fly - midge, gnat or mosquito | Culicoides vexans | a biting midge | 3 | 1997 |
| true fly - midge, gnat or mosquito | Culiseta | a Culiseta mosquito (unidentified) | 28 | 2013 |
| true fly - midge, gnat or mosquito | Culiseta annulata | a mosquito | 18 | 2021 |
| true fly - midge, gnat or mosquito | Culiseta fumipennis | a mosquito | 1 | 1978 |
| true fly - midge, gnat or mosquito | Culiseta morsitans | a mosquito | 1 | 1999 |
| true fly - picture-winged, conopid or stilt-legged fly | Campiglossa absinthii | a gall fly | 2 | 2004 |
| true fly - picture-winged, conopid or stilt-legged fly | Chaetorellia jaceae | a gall fly | 1 | 2021 |
| true fly - picture-winged, conopid or stilt-legged fly | Chaetostomella cylindrica | a gall fly | 20 | 2019 |
| true fly - picture-winged, conopid or stilt-legged fly | Chetostoma curvinerve | a gall fly | 4 | 2018 |
| true fly - picture-winged, conopid or stilt-legged fly | Conops flavipes | a fly | 3 | 2003 |
| true fly - picture-winged, conopid or stilt-legged fly | Conops quadrifasciatus | a fly | 36 | 2019 |
| true fly - picture-winged, conopid or stilt-legged fly | Conops strigatus | a fly | 1 | 1973 |
| true fly - robber, empid or dolichopid fly | Campsicnemus curvipes | a dolichopodid fly | 31 | 2021 |
| true fly - robber, empid or dolichopid fly | Campsicnemus loripes | a dolichopodid fly | 2 | 2002 |
| true fly - robber, empid or dolichopid fly | Campsicnemus scambus | a dolichopodid fly | 2 | 2009 |
| true fly - robber, empid or dolichopid fly | Chelifera precatoria | a dance fly | 3 | 2001 |
| true fly - robber, empid or dolichopid fly | Chrysotimus flaviventris | a dolichopodid fly | 8 | 2020 |
| true fly - robber, empid or dolichopid fly | Chrysotimus molliculus | a dolichopodid fly | 1 | 2000 |
| true fly - robber, empid or dolichopid fly | Chrysotus blepharosceles | a dolichopodid fly | 11 | 2020 |
| true fly - robber, empid or dolichopid fly | Chrysotus cilipes | a dolichopodid fly | 6 | 1983 |
| true fly - robber, empid or dolichopid fly | Chrysotus cupreus | a dolichopodid fly | 4 | 2021 |
| true fly - robber, empid or dolichopid fly | Chrysotus femoratus | a dolichopodid fly | 1 | 2006 |
| true fly - robber, empid or dolichopid fly | Chrysotus gramineus | a dolichopodid fly | 55 | 2013 |
| true fly - robber, empid or dolichopid fly | Chrysotus neglectus |