Efferia sp. Maybe

Man. Where’s a key to the genera of Asilidae? Like how does an average amateur entomologist determine what’s Efferia versus, say, Promachus? Huh! Now I espy that many actually split the genus Efferia. Huh!

This fly has turned up in the backyard to be documented, two years running. I don’t really even know its genus. But it’s a big fly, over an inch long

So that was yesterday afternoon. This morning an obviously different fly of the same likely species turned up in precisely the same spot that the other fly was in yesterday. This one though is a male. I believe it is slightly littler than the female.

Are these flies separating themselves temporally? Will they ever get together and have maggots? Are they really the same species? Where does this highway lead to?