Moved from Exoprosopa.

I believe this is the west coast form of Exoprosopa fascipennis. This fly is patchily distributed in sandy locales throughout the southern 2/3 of the US and most of Mexico. It takes on many forms throughout that range (compare the wing pattern to Eastern forms). It has a highly distinctive and unvariable male genitalia, but it may ultimately prove to be a species complex. At present, I don't see good reason to start making names for the races. This almost black form with bold white bands is characteristic of the CA coast form, perhaps an adaptation to improve solar absorption in the marine layer environment.

Moved from Bee Flies.