Window Fly

Hermetia fly?
Location:  Redding, California, United States, North America
October 2, 2010 6:18 pm
Hey, my roommate caught this fly and I can’t figure out what it is. Short anennae, maybe 3 segments. The hindtibia are half white and half black, and the foretarsus, midtarsus, and hindtarsus are all white. Interestingly, there only appears to be 4 abdominal sternites, the first of which, appearing where the 1st and 2nd usually would be, is transparent/white. The rest of the body, including the wings, is black, or very nearly so, excepting the halters, which are a cotton candy/bread-mold blue. It looks very similar to certain wasps that live in this area, and often opens it’s wings to a position similar to bees or waspsso I thought it might be in the family Hermetia, but I haven’t been able to find a picture that matches this fly. Do you have any idea what it is?
Signature:  Collegiate ameture

Dear Collegiate ameture,
You are absolutely correct.  Your fly is a Black Soldier Fly, Hermetia illucens, though we prefer the name Window Fly, a name not recognized on BugGuide.  We use the name Window Fly which was reported by Charles Hogue in his excellent book, Insects of the Los Angeles Basin, and the name refers to the transparent “windows” on the abdomen that you describe.  BugGuide uses Window Fly for an entirely different family.