Attack rates, progeny production, sex ratios, and host use efficiency of Muscidufurax raptor Girualt and Sanders, Spalangia cameroni Perkins, S. endius (Walker), S. nigroaenea Curtis, S. gemina Boucek (Hymenoptera: Pteromalidae), and Dirhinus himalayanus (Hymenoptera: Chalcididae) were evaluated in laboratory bioassays with five dipteran hosts: house fly (Musca domestica L.), stable fly (Stomoxys calcitrans L.), horn fly (Hematobia irritans L.), black dump fly [Hydrotaea aenescens (Weidemann)] (Diptera: Muscidae), and a flesh fly (Sarcophaga bullata Parker) (Diptera: Sarcophagidae). M. raptor, S.cameroni, and S. endius readily attacked and produced progeny on all five host species, with substantially lower production from S. bullata than from the muscid hosts. Rates of host attacks by S. nigroaenea and S. gemina were similar on house fly, stable fly, and black dump fly hosts, with lower rates on horn fly; almost no progeny were produced by S. nigroaenea on S. bullata hosts. D. himalayanus, a large-bodied chalcidid parasitoid, had highest rates of host attacks and progeny production on S. bullata and H. aenescens, followed by stable fly and house fly hosts; very few progeny were produced by this species on horn fly hosts. Overall differences among different geographic strains of parasitoids (from Russia, Kazkhstan, and Florida) were generally small, although the Florida strain of M. raptor was superior to the two Eurasian strains.