Female Nasonia vitripennis (Walk.) parasitizing housefly (Musca domestica L.) pupae produce a smaller percentage of female progeny at high parasite:host ratios than at lower ones because they fertilize a smaller percentage of their eggs (in this species unfertilized eggs produce male progeny), and because more female than male larvae die on superparasitized hosts. The adult females fertilize relatively fewer eggs at high than at low parasite:host ratios for two reasons. First, they encounter relatively more previously attacked hosts, on which they lay a smaller percentage of fertilized eggs than on previously unattacked ones; second, they more often encounter other female parasites while ovipositing, and this interference reduces the percentage of fertilized eggs they lay.

Females of Nasonia vitripennis (Walk.) (Hymenoptera: Pteromalidae) laid fewer eggs on parasitized than on unparasitized pupae of the house fly, Musca domestica L. 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.

Can. Ent. 111: 1337-1344 (1979) A study on techniques for rearing Glischrochilus quadrisignatus (Say) in the laboratory showed that provision of adequate moisture and control of fungal diseases were essential. Most field-collected adult females oviposited regardless of when the collections were made, but there were large variations in the preoviposition periods. Hibernating beetles collected in the spring had a much shorter preoviposition period than beetles collected in the autumn and early winter. The high viability of eggs laid by overwintering females kept separate from males indicated that the beetles mated in the fall. Three consecutive generations occurred when beetles were reared in crocks supplied with corn and tomatoes in a greenhouse. At 21°C, the incubation period for eggs averaged 4.1 days, the larval period 21-22 days, and the pupation period 11.8 days. Newly developed adults remained in the soil for an average of 11.2 days before emerging.

Adults of most species of insect parasites spend much time finding objects that influence their individual and collective well-being. The object found at any time is usually correlated with the physiological state of the parasite and with extrinsic factors existing at that time. From the standpoint of the species' economy, the most important objects to be discovered are hosts on which fertile parasite progeny can mature. Whether hosts are found and parasitized is influenced, to varying degrees with different parasite species, by whether the female has already found, or been found by, a male of the same species, and by whether she has already located food other than that provided by hosts. The present study is of factors that affect host finding by females of a pteromalid, Nasonia vitripennis (Walk.).

Pimpla turionellae (L.) (= exarainator F.) is a pupal parasite of many species of Lepidoptera. During propagation of this species for release in Canada against the European pine shoot moth, Rhyacionia buoliana (SCHIFF.), and the spruce budworm, Choristoneura ]umi]erana (CL~.M.), data were obtained oil the influence of the size of the host pupae on sex ratio, development time, and size of the adults. Material and MethodsMated females of P. turio~ellae that had been reared in the laboratory on a number of medium-sized hosts were plaeed singly in cages that measured 4 • 4 • 2 1/2 inches. They were fed daily a 10 per eent solution of honey and sprayed twiee daily with tap water. Pupae of different hosts were introduced into the cage and eaeh was removed as soon as the parasite had laid one egg on it. The hosts were then weighed, placed singly in glass vials, and incubated at 22-24 oC. and 60 q-5 per cent relative humidity. Weight was used as a measure of host size because of differences in shape between moth and butterfly pupae. When the parasites emerged they and the host remains were weighed separately. As this species is arrhenotokous, only data from females that produced both males and females were used. Pupae that did not produce parasites were dissected.Nine speeies of lepidopterous hosts were used. Anagasta k4~hniella (ZELL.) and Galleria mellonella (L.) (Pyralidae) were taken from labo-