Psyttalia cosyrae (Wilkinson) (Hymenoptera: Braconidae) is a synovigenic, koinobiont larval-pupal parasitoid of Ceratitis cosyra (Walker) (Diptera: Tephritidae), and possibly other tephritid fruit flies. Host acceptance and suitability of medfly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), mango fruit fly, Ceratitis cosyra, Natal fruit fly, Ceratitis rosa Karsch, Ceratitis fasciventris (Bezzi), Ceratitis anonae Graham, and melon fruit fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), for oviposition and development of this parasitoid were investigated. The effect of different host species on traits widely used to assess parasitoid fitness was also evaluated. Psyttalia cosyrae accepted all host species tested, but acceptance varied. In no choice tests, C. cosyra and C. capitata were accepted at a significantly higher rate than the other four species. The parasitoid successfully developed only in C. cosyra and C. capitata. Eggs oviposited in C. rosa, C. fasciventris, C. anonae, and B. cucurbitae were encapsulated. Developmental time was shorter in C. capitata than in C. cosyra, but parasitoid progeny emerging from the latter host were more fit, as measured by percent female progeny, adult size, egg load, and adult survival. none