FREQUENCY AND VIABILITY OF DIPLOID AND HAPLOID MALES OFFSPRINGS OF MATED FEMALES OF SOLITARY ENDOPARASITOID (DIADROMUS PULCHELLUS ) ( ICHNEUMONIDAE) .

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

Y a-t-il élimination d'Eupelmus orientalis Crawford par Eupelmus vuilleti Crawford (Hymenoptera : Eupelmidae) des systèmes de stockage du niébé (Vigna unguiculata Walp) ?

Niébé is a food leguminous plant cultivated in tropical Africa for its seeds rich in proteins. The main problem setted by its production is the conservation of harvests. In the fields as in the stocks, the seeds are destroyed by pests (bruchids). These bruchids are always associated with several entomophagous species of hymenoptera. Four entomophagous species were listed : an egg parasitoid (U lariophaga Stephan), and three solitary larval and pupal ectoparasitoids (D. Basalis Rondoni, Pteromalidae; E. vuilleti Crawford and E. orientalis Crawford, Eupelmidae). The survey of the populations shows that at the beginning of storage, E orientalis is the most abundant specie (72 %) whereas E. vuilleti and D. Basalis respectively represent 12 % and 16 % of the hymenoptera. During storage, the E orientalis population decreases gradually and it disappears completely in less than two months after the beginning of storage. E. Vuilleti population becomes gradually more important than D. basalis population which regress until less than 10 % of the emerging parasitoids. E vuilleti adopts ovicide and larvicide behaviour against D. Basalis. This behaviour explains its population regression inside granaries. If the aggressive behaviour of this Eupelmidae is a constant, that could also explain the disappearance of E orientalis. However if this species is maintained in stocks, it would be an effective control agent of bruchids according to their parasitic capacities. This study shows that ovicide and larvicide behaviour of E vuilleti is not expressed against E orientalis. When the females have exclusively the hosts already parasitized by E orientalis, they do not lay eggs. The disappearance of E orientalis could not thus be explained by the presence of E. vuilleti

The potential of mass rearing of Monoksa dorsiplana (Pteromalidae) a native gregarious ectoparasitoid of Pseudopachymeria spinipes (Bruchidae)in South America

In Chile and Uruguay,the gregarious Pteromalidae (Monoksa dorsiplana) has been discovered emerging from seeds of the persistent pods of Acacia caven attacked by the univoltin bruchid Pseudopachymeria spinipes. We investigated the potential for mass rearing of this gregarious ectoparasitoid on an alternative bruchid host, Callosobruchus maculatus, to use it against the bruchidae of native and cultured species of Leguminosea seeds in South America. The mass rearing of M.dorsiplana was carried out in a population cage where the density of egg-laying females per infested seed was increased from 1:1 on the first day to 5:1 on the last (fifth) day. Under these experimental conditions egg-clutch size per host increased, and at the same time the mortality of eggs laid also increased. The density of egg-laying females influenced the sex ratio which tended towards a balance of sons and daughters,in contrast to the sex ratio of a single egg-laying female per host (1 son to 7 daughters). The mean weight of adults emerging from a parasitized host was negatively correlated with the egg-clutch size, i.e., as egg-clutch size increased, adult weight decreased. All these results show that mass rearing of the gregarious ectoparasitoid M.dorsiplana was possible under laboratory conditions on an alternative bruchid host C.maculatus. As M.dorsiplana is a natural enemy of larval and pupal stages of bruchidae, the next step was to investigate whether the biological control of bruchid C.maculatus was possible in an experimental structure of stored beans

Facultative Hyperparasitism: Extreme Survival Behaviour of the Primary Solitary Ectoparasitoid, Dinarmus basalis

This study investigated the egg-laying behaviour of ectoparsitoid, Dinarmus basalis Rondani (Hymenoptera: Pteromalidae), females when faced with a prolonged deprivation of suitable hosts leading to extreme ‘oviposition pressure’. The egg-laying behaviour of virgin D. basalis females was tested with Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) hosts previously parasitized by the conspecific females in which the developing larvae had reached the last larval instar (L5) or pupae. The hyperparasitism did not prevent the occurrence of superparasitism, but only one D. basalis egg from a hyperparasitized D. basalis L5 larvae reached the adult stage due to the solitary behaviour of the D. basalis larvae. Under these experimental conditions, 60.78% of the D. basalis adults emerging from larvae were miniaturized due to the depletion of host resources

Reproductive capacity of females Eupelmus vuilleti (Eupelmidae) inseminated by hyperparasitoid males developed upon the primary parasitoid Dinarmus basalis (Pteromalidae).

Eupelmus vuilleti is a primary and solitary ectoparasitoid of the larval stages of Bruchids (Callosobruchus maculatus, Bruchidius atrolineatus). In a context of intense competition for healthy hosts, E. vuilleti displays ovicide and larvicide behaviours towards the Pteromalid D. basalis during its development (kleptoparasitism), and in an extreme expression of kleptoparasitism the E. vuilleti females hyperparasitize the final larval stage (L5 stage) of D. basalis. In this study, we compared the variability of reproductive success in males that had developed in the context of hyperparasitism to that in males that had developed on primary hosts. The adaptation capacity of the males when 24 h old was analysed in terms of their weight, of the quantity of spermatozoids stored in the seminal vesicles, of the quality of insemination determined from the quantity of spermatozoids stored in the spermatheca of the females after the first mating, and of the number of daughters produced. Adults of E. vuilleti, the larvae of which had developed as hyperparasitoids, are smaller than those that have developed on primary hosts, but they keep all the abilities required to parasite a population of primary hosts once the competitive pressure is reduced

Consequences of infanticide for a gregarious ectoparasitoid of leafroller larvae

1. In this laboratory study, the clutch size and handling time of Goniozus jacintae were investigated, a comparison of its life-history performance between primary and secondary (laid after infanticide events) broods was carried out, and the lipid and protein concentrations in the haemolymph of non-parasitised and parasitised hosts were estimated. 2. It was found that G. jacintae temporarily paralysed its host larvae for 66 min and briefly guarded its brood for 66 min. The clutch size of G. jacintae increased from two to seven with increasing larval fresh weight of its host, and both ovicide and larvicide of primary clutches occurred in 81% of encounters. 3. Secondary clutches of G. jacintae were significantly larger than primary clutches in two of three ovicide treatments for the same host individuals. Secondary clutches also experienced greater brood survivorship than primary clutches. 4. Lipid concentrations were consistently higher in the haemolymph of parasitised hosts, and protein concentrations were initially higher (until egg hatch), but increased at a lower rate in parasitised hosts than in non-parasitised hosts. 5. This study is the first to provide evidence that improved nutritional quality could be an important benefit of infanticide for an insect parasitoid, allowing for larger clutch size and improved brood survivorship among secondary broods