Mellininae is a small subfamily about which not much is known. There are only 17 described species in two genera. Several species make their burrows in sandy locations and provision them with adult Diptera (Clausen 1940/1962).
This group was placed in the Mellinidae in the Apoidea by Finnamore & Michener (1993) . There at least 10 species in one genus . They are predators on muscoid Diptera, usually around animal excrement.
A key reference is Bohart & Menke (1976).