Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Has photo thumbnails, distribution maps, and some life history information. Be cautious in interpreting the distribution maps.
http://www.npwrc.usgs.gov/resource/distr/insects/dfly/dflyusa.htm

most of USGS sites are now defunct incl this one...
site es no mas...

another adjustment please
the site explicitly asks to cite the resource a certain way; we should honor that. pls add "..., by Boris C. Kondratieff (coordinator)" to the title, i think that would be fine