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

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

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

Bases immunológicas de las relaciones hospedero – parasitoide

Como para todo parásito obligatorio, el éxito reproductivo o fitness de un parasitoide depende en gran medida de su capacidad de infestar con éxito a su hospedero. Este éxito parasitario se descompone generalmente en cuatro etapas sucesivas: la localización del hábitat, la localización del hospedero, la aceptación del hospedero y la adecuación a la fisiología del hospedero (Doutt, 1964; Vinson, 1975). Para cada una de esas etapas, un conjunto de adaptaciones morfológicas, de comportamiento y/o fisiológicas han sido seleccionadas en el curso de la evolución de modo a optimizar el éxito reproductivo del parasitoide. Por el contrario, el éxito reproductivo del hospedero va a depender de su capacidad para escapar al parasitismo. Así, para cada una de las etapas claves del parasitismo un conjunto de adaptaciones que permitan al hospedero escapar al mismo puede ser seleccionado. En consecuencia, el resultado de la interacción entre un parasitoide y un hospedero va a depender de un conjunto de adaptaciones y de contra adaptaciones de parte de cada uno de los dos Bases immunológicas de las relaciones hospedero – parasitoide Capítulo 5 Danielle ROJAS-ROUSSE 60 componentes de la asociación. El conjunto de esas adaptaciones se traduce por la capacidad del parasitoide de invadir a su hospedero y por la capacidad del hospedero de reaccionar contra los parasitoides