Coremacera marginata 
Coyote brush bud gall midge 
Craneiobia tuba 
Creosote gall midge 
Cricotopus bicinctus 
Cricotopus sylvestris 
Cricotopus tremulus 
Ctenophora elegans 
Ctenophora ornata 
Culiseta annulata 
Cuterebra austeni 
Cylindromyia bicolor 
Cylindromyia brassicaria 
Cylindromyia intermedia 
Cylindromyia interrupta 
Cyrtodiopsis whitei 
Cyrtopogon longimanus 
Dalmannia aculeata 
Daptolestes limbipennis 
Dark Giant Horsefly 
Dark-winged Chrysogaster 
Dark-winged fungus gnat 
Dasineura crataegibedeguar 
Dasineura pilosa