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Summary: Sixty-three species of insect parasites of the winter moth,Operophtera brumata (L.) (Lepidoptera: Geometridae), including 26 reared in the present investigation and 37 recorded only in the literature, are listed. Eleven of those reared in the present study are new parasite records for winter moth. Thirteen of the records from the literature are questionable because in each case the identity of either the parasite or host in uncertain. Notes on distribution and life-history are given for species reared in the present study.

Zusammenfassung: Das Geschlechter-Verhältnis vonPimpla turionellae (L.) (Hymenoptera: Ichneumonidae) — einem Parasiten vieler Lepidopteren-puppen — hängt von der Grösse des Wirtes ab, in welchem der Parasit sich entwickelt. In einem kleinen Wirt, wieAnagasta kühniella (Zell.) (Pyralidae), entwickeln sich nur die Männchen. In einem mittelgrossen Wirt, wiePyrausta nubilalis (Hbn.),Galleria mellonella (L.)(Pyralidae), Pieris rapae (L.) (Pieridae), undTrichoplusia ni (Hbn.) (Noctuidae), entstehen Weibchen und Männchen in gleicher Zahl. In grossen Puppen vonAglais milberti Latr.(Nymphalidae), Malacosoma americanum (F.) (Lasiocampidae) undDanaus plexippus L. (Danaidae) entwickeln sich mehr Weibchen. Im allgemeinen dauerte die Entwicklung in grösseren Puppen viellänger als in kleinen. Das Gewicht des Parasiten nimmt zu mit dem Gewicht des Wirtes Die schwersten Männchen wiegen ungefähr neun mal mehr als die leichtesten.

AbstractFemales of Nasonia vitripennis(Walk.) (Hymenoptera: Pteromalidae) discriminate between unparasitized housefly pupae (Musca domesticaL.) and those parasitized by either Muscidifurax raptorG. & S. or Spalangia cameroniPerk. (Hymenoptera: Pteromalidae) and lay fewer eggs on parasitized hosts. Oviposirion restraint is more pronounced towards hosts attacked by M. raptorthan towards those attacked by S. cameroni, but less than that exhibited towards pupae previously parasitized by N. vitripennis. Damage to the fly pupae, from piercing by the female?s ovipositor and probably also from a "venom" injected by the female, is responsible for inter- as well as ultra-specific discrimination and restraint.

AbstractDevelopment time for the parasite Nasonia vitripennis(Walk.) was shorter on young pupae (less than 48 hours old at 24.5 ± 0.5 °C) than on older pupae of the house fly, Musca domesticaL. This was primarily because of intrinsic differences between young and old house-fly pupae as hosts. Though less important, two other conditions in young hosts favoured a shorter mean development period for N. vitripennis: first, the smaller proportion of very small parasites, which mature more slowly than the larger ones; and, second, the greater number of parasite larvae per host, which is associated with more rapid development in this species.

AbstractMortality of immature Nasonia vitripennis(Walk.) was least on young house fly pupae (less than 48 hours old, at 24.5 ± 0.5 °C.) and increased with increasing host age. Increased mortality on old hosts was manifested principally as a decrease in female adult progeny, numbers of adult males and of mature diapause larvae remaining approximately constant. Reduction in the percentage of females in the adult progeny reared on old hosts probably resulted from superparasitism. This kills more female than male larvae and occurred more commonly on old hosts, each of which provides a smaller quantity of suitable food for the immature parasites. Adults reared on old hosts were smaller and relatively fewer of them were able to emerge. The proportion of the total mature parasite progeny that remained in diapause was greater on old hosts, probably because of qualitative differences in the food provided by hosts of different ages.

AbstractOne larval parasite, Aphaereta pallipes(Say) (Hymenoptera: Braconidae), and three pupal parasites (Muscidifurax raptorG. & S., Spalangia nigraLatr., and Eupteromalus dubius(Ashm.) (Hymenoptera: Pteromalidae)) developed on face fly, Musca autumnalisDe G. (Diptera: Muscidae), collected near Belleville, Ont. These parasites, and four other Hymenoptera and one staphylinid, were reared from other Diptera associated with M. autumnalis. The economic value of the four face fly parasites is limited because only one (A. pallipes) finds hosts easily, none is host-specific, and few individuals that develop on face fly pupae emerge from the puparia.

AbstractOnly one parasite species survived on most housefly (Musca domesticaL.) pupae multiparasitized by any two of Nasonia vitripennis(Walk.), Muscidifurax zaraptorK. & L., or Spalangia cameroniPerk. N. vitripennisand M. zaraptorwere both intrinsically superior to S. cameroniif the attacks on the hosts by their females preceded, were simultaneous with, or followed by up to 48 hours those by females of S. cameroni. N. vitripenniswas intrinsically superior to M. zaraptorif its attack preceded that by M. zaraptorby at least 24 hours; M. zaraptorsurvived when it oviposited before N. vitripennis; and neither species was consistently superior to the other when their attacks were simultaneous or that by N. vitripennisclosely preceded that by M. zaraptor. N. vitripennisoften survived on multiparasitized hosts because of its rapid development and rapid and thorough host utilization which caused its rivals to starve. In contrast, M. zaraptor?ssuccess was a consequence of its pr?dation on eggs and larvae of its competitors and to a lesser extent its moderately rapid development and host utilization. S. cameroniwas usually intrinsically inferior to both of the other species because, in spite of being predaceous on their larvae, it developed much more slowly and seldom attacked their eggs. The significance of these qualitative characteristics in insect parasites used in biological control programmes is discussed.

AbstractFemales of Spalangia cameroniPerk, use the ovipositor to differentiate between unparasitized and parasitized housefly (Musca domesticaL.) pupae; and prefer to lay on unparasitized hosts instead of those attacked by S. cameroni, Nasonia vitripennis(Walk.), or Muscidifurax zaraptorK. & L. (Hymenoptera: Pteromalidae). The intensities of oviposition restraint on the three kinds of attacked hosts are similar. Changes in parasitized pupae to which the female parasites react probably involve "venoms" injected by each species during oviposition.

AbstractFemales of Muscidifurax zaraptorK. & L. oviposit on unparasitized housefly (Musca domesticaL.) pupae in preference to those attacked by M. zaraptor, Nasonia vitripennis(Walk.), or Spalangia cameroniPerk. (Hymenoptera: Pteromalidae). The discrimination against parasitized houseflies is greatest in the case of those attacked by M. zaraptorand least for those parasitized by S. cameroni. Discrimination is based on differences between unparasitized and parasitized pupae that the female parasites detect after they pierce the pupae with the ovipositor. Death of parasitized hosts, or a change resulting directly therefrom, is not responsible for the differences. The fact that hosts pierced at or near the original drilling site are more likely to be rejected than those attacked elsewhere supports the hypothesis that a ?venom? injected by the female parasites during oviposition diffuses throughout the host and is responsible for oviposition restraint.

AbstractFemales of Nasonia vitripennis(Walk.) (Hymenoptera: Pteromalidae) laid fewer eggs on parasitized than on unparasitized pupae of the house fly, Musca domesticaL. Chemical and/or physical conditions of parasitized pupae are detected by the female?s ovipositor, causing this restraint. These conditions may in part result from the host?s death, caused by earlier parasitization, but other factors are also involved. These may include venom injected by the female parasite before she lays, and internal injury to the host resulting from insertion of the parasite?s ovipositor. The female parasite does not discriminate because of physical or chemical traces on the surface of parasitized puparia, of eggs or a surface wound on the pupa, or of absence of heart beat in the pupa.

AbstractSuperparasitism created a food shortage and thereby reduced survival and size of adult Nasonia vitripennis(Walk.) (Hymenoptera: Pteromalidae) reared on pupae of the house fly, Musca domesticaL. Superparasitism also reduced the percentage of females in the adult progeny but had no effect on rate of development, ability to emerge, or incidence of diapause in N. vitripennis.