On the Life-history of Melittobia acasta, Walker; a Chalcid Parasite of Bees and Wasps

Abstract

Melittobia is a chalcid, ectoparasitic upon a number of species of Hymenoptera and upon the pupae of certain flies. The insect was bred in the laboratory and the life-history is described in detail.A number of experiments were made with regard to possible hosts and as to feeding and reproduction and certain points are of some interest.For instance, the male apparently does not feed but the female uses her ovipositor with which she punctures the eggs, larvae or pupae of various insects, afterwards sucking the blood which oozes from the puncture. Such eggs, larvae or pupae, in spite of repeated punctures, may continue to develop.Before beginning oviposition upon the surface of a suitable host, the female punctures the host one or more times with her ovipositor and apparently injects an anaesthetizing fluid, since insect larvae and pupae, upon which eggs have been laid, very rarely develop farther and yet remain fresh for a considerable time extending to many months.With regard to reproduction, inbreeding appears to be normal, mating usually taking place between two individuals of the same brood and later between the female and one of her own offspring. Virgin females, unable to find a male, lay a few eggs, which always produce males, the first of which to emerge mates with the female.The female is very prolific and may lay as many as twelve hundred eggs in two or three batches, mating taking place before each batch is laid. The last eggs of a batch are almost invariably male eggs, indicating that the female has exhausted her supply of spermatozoa.A virgin female, whose eggs are removed so that she cannot rear a mate, may lay as many as ninety eggs during her life-time, her length of life being more than doubled, and such a female will survive through the winter, even withstanding frost, whereas fertilized females apparently all die in October or November at the latest.All the eggs of a virgin female are apparently capable of developing and all such eggs produce males.