This rather plump Zelia
was hanging very closely about a dead stump (a plum) in my yard. (An advantage of not having a neat yard and neighbors who are not fussy--interesting insects.) Possibly this was a female looking for whatever its host is. Size estimated.
My guess is this is indeed Z. vertebrata, and that this was a female looking for a host: Brimley, p. 367 (1)
, states that Zelia vertebrata
parasitizes the "Betsy Beetle (Passalus cornutus)", which is now called Odontoaenius disjunctus
The standing, decaying stump this fly was frequenting is a good habitat for the likely host beetle--abundant in my yard.