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Anthrax analis
Jet black hoverfly with interesting pattern on wings, was skirting the ground as if searching leaf litter until came to rest, then gust of wind and it was gone. A. analis is a parasitoid of fire beetle larva, eggs are deposited near the beetle's burrow, the fly larva then enters attaching to host and overwinters there. When host pupates in spring, fly larva cuts through skin and competes growth as internal parasite.
I believe you are correct Forest, this would explain it's behavior, since the area sighted had greatest concentration of fire beetles on property earlier in the year.
I agree that this is a Bee Fly. Possibly Anthrax georgicus. Sometimes they can be a bit tricky to ID.
http://bugguide.net/node/view/95586
See what you think.