ANALYSIS OF THE REPRODUCTIVE POTENTIAL OF DIPLOID MALES IN THE WASP DIADROMUS-PULCHELLUS (HYMENOPTERA, ICHNEUMONIDAE)

In the ichneumonid wasp Diadromus pulchellus (Wesmael), diploid males may regularly be produced in laboratory populations by inbreeding. The y are viable, produce diploid sperm and are equally capable of multipl e inseminations as are haploid males. Their spermatozoa are also able to penetrate the oocyte. Progeny sired by diploid males are essentiall y haploid sons with only a few daughters. The sons are normal haploid individuals, produced in a frequency significantly higher than in cros ses between females and haploid males. The daughters are normal diploi d females probably resulting from the fertilization of an oocyte by an exceptional haploid sperm rarely produced by diploid males. Triploid individuals were not observed and their absence was correlated with th e high mortality observed during the first developmental stages. The d eath of these individuals is discussed in the light of the phenomenon of superparasitism to explain the increase in the frequency of sons pr oduced in crosses with diploid males. Despite their viability, their a bility to produce sperm and their normal potential insemination, diplo id males of Diadromus pulchellus are therefore almost sterile.