Frequency and Viability of Diploid and Haploid Males Offsprings of Mated Females of Solitary Endoparasitoid (DIADROMUS Pulchellus) (Ichneumonidae)

Abstract

Sex determination in the order Hymenoptera is based on arrhenotoky, hymenopteran males are usually haploid and females diploid. Males of the Ichneumonidae Diadromus pulchellus, solitary endoparasitoid of A. assectella pupae are normally haploid, but diploid males are present in a natural population and can be obtained in a experimental population. The future of an ovocyte laid by mated females of the solitary endoparasitoid Diadromus pulchellus was characterised by 6 probabilities related to the sex and the development of the ovocyte. The probabilities of fertilisation of female ovocyte (k1) or non-fertilisation (k3) showed that an inseminated female functioned as a unmated female for half of the time (since k1= 0.492 and k3 = 0.455) with the probability of fertilisation of male ovocyte (k2 = 0.053).The survival probabilities of each type of ovocyte showed that an ovocyte had a high probability of developing up to the adult stage, although the difference between the calculated sex ratios at laying (males / females = 1.032) and at emergence (0.90) revealed a slight reduction in the number of haploid sons. The probabilities of fertilisation and of viability of all the ovocytes laid by each of the 33 mated females were analysed by an ascending hierarchical classification of Euclidean distances and by an analysis of their principal components. The 33 mothers were distributed into 4 distinct sub-groups characterised by a sex ratio varying from an exclusive presence of females to an exclusive presence of males. Our hypothesis was that this distribution in 4 sub-sets could not simply result from the random nature of the sample.