Flies are shown alphabetically within taxonomic level. If you see an error, please let me know via the contact tab at the top of the page.
Bombyliidae: Bee Fly (Villa)
According to BugGuide, "This genus has not been reviewed in NA [North America] since Coquillett (1892) and needs revision based on genitalic characters." I'll leave it to someone else to look at the genitalia of the 200+ species of Villa.
Cecidomyiidae: Gall Midge (Asphondylia)
Cecidomyiidae: Willow Pinecone Gall Midge (Rabdophaga strobiloides)
Cecidomyiidae: Wooly Bud Gall Midge (Rhopalomyia medusirrasa)
These galls are on a species that I have tentatively identified as Artemisia dracunculus. You can see those plants earlier in the growing season by visiting my page on the Aster family and scrolling down. Littlefield and Burns show two images of these galls in the lower right corner of their page on A. dracunculus but don't explain what they are.
Syrphidae: Hoverfly (Eristalis)
Syrphidae: American Hoverfly (Eupeodes americanus)
Syrphidae: Hoverfly (Paragus haemorrhous)
The long, thin abdomen on this hoverfly, compared to many other fly species, makes it look just a bit like a wasp.
Tachinidae: bee-like Tachinid Fly (Hystricia?)
My photos show some tachinid flies with yellow abdomens, others with red ones. No idea what the difference indicates.
Tephritidae: Rabbitbrush Gall (Aciurina trixa)
Ulidiidae: Picture-Winged Fly (Chaetopsis)
At first glance this looked like a bee. But not only does it have a fly head, the black and yellow stripes are on the wings not the abdomen.