The endoparasitoid Coptera haywardi (Ogloblin) (Diapriidae) was discovered in Mexico attacking the pupae of the Mexican fruit fly, Anastrepha ludens (Loew). Typically, parasitoids of Diptera Cychlorrhapha pupae develop as ectoparasitoids and are generalists that attack hosts in a number of families. Aspects of the bionomics of C. haywardi were compared to those of two chalcidoid ectoparasitoids, Dirhinus himalayanus Westwood and Spalangia gemina Boucek. C. haywardi developed in three genera of Tephritidae, but not in species of other families. The two species of chalcidoids developed in all the calypterate and acalypterate hosts to which they were exposed. In an olfactometer C. haywardi preferred Anastrepha suspensa (Loew) pupae, while the chalcidoids preferred the pupae of Musca domestica L. This preference in S. gemina was diminished in insects that had been reared of A. suspensa. C. haywardi oviposited in the A. suspensa pupae that had been previously parasitized by the braconid Diachasmimorpha longicaudata (Ashmead). However, it completed development only in unparasitized pupae. Mortality of the primary parasitoid due to D. himalayanus was approximately two-thirds the mortality inflicted on the host fly. S. gemina did not discriminate between parasitized and unparasitized pupae of A. suspensa and developed in both. C. haywardi appears to have a more restricted host range relative to chalcidoid pupal parasitoids and this may be due to its endoparasitic development. none