Analysis of multiparasitism by Eupelmus vuilleti (Craw) (Eupelmidae) and Dinarmus basalis (Rond) (Pteromalidae) in the presence of one of their common hosts, Bruchidius atrolineatus (Pic) (Coleoptera Bruchidae)

Abstract

Bruchidius atrolineatus (Pic) is a tropical beetle (Coleoptera Bruchidae) that develops during the larval and pupal stages in the seeds of a legume Vigna unguiculata (Walp). Two species of Hymenoptera, Dinarmus basalis (Rond) and Eupelmus vuilleti (Craw), solitary ectoparasitoids of the larvae and pupae of B. atrolineatus, were introduced successively in the presence of their hosts, varying the interval between the two introductions. When D. basalis females were introduced 24 h, 3 days or 7 days after E. vuilleti, multiparasitism was low. The females had low fecundity, and their eggs were not distributed randomly over the different available hosts. When E. vuilleti females were introduced second, they oviposited on the different hosts availabe and did not avoid multiparasitism. The presence of hosts already parasitised by D. basalis increased the reproduction of E. vuilleti, and the fecundity of the females was higher than in control batches with E. vuilleti alone. E. vuilleti seems capable of detecting the ovipositor shafts drilled by the D. basalis females, and by introducing its own ovipositors killing the D. basalis eggs or larvae. When interspecific competition was occurring the number of E. vuilleti adults emerging from the seeds was no different from that observed in control batches with E. vuilleti alone, and there were always fewer D. basalis adults than in control batches (D. basalis alone). This interspecific competition reduces the influence of the two parasitoids in the biological control of bruchid populations.

Host marking behavior in phytophagous insects and parasitoids

“…Whether or not interspecific discrimination might arise and be maintained in a situation in which species differ in competitive abilities (perhaps a more common situation) has not, to our knowledge, been considered theoretically. One might anticipate that an inferior competitor will discriminate more against use of a host occupied by a superior competitor's offspring than the reverse and, in fact, this generally appears to be the case (Bolter & Laing, 1983;Giga & Smith, 1985;McBrien & Mackauer 1991;Leveque et al, 1993). In bruchid beetles, an asymmetry in interspecific discrimination is mediated by an asymmetry in one species' response to the other species' MP.…”

The effect of multiple parasitism by an endoparasitoid on several life historytraits of leafminer ectoparasitoids

“…In many studies on interspecific interaction between parasitoids, several kinds of competition avoidance mechanisms by the inferior species have been reported (e.g., McBrien and Mackauer, 1989;van Alebeek et al, 1993;Leveque et al, 1993;Gauthier et al, 1999). On the other hand, competition avoidance by superior species has not been observed.…”

“…On the other hand, competition avoidance by superior species has not been observed. Such an asymmetric response to interspecific competition has been explained by a difference in survival rate between winner and loser (e.g., van Alebeek et al, 1993;Gauthier et al, 1999). However, almost no studies have measured 318…”

“…Many researchers have noted such competitive relationships between solitary parasitic wasps (e.g., Leveque et al, 1993;Gauthier et al, 1999). Interestingly, interspecific competition is highly asymmetric in almost all parasitoid-parasitoid combinations reported (e.g., Leveque et al, 1993;Gauthier et al, 1999). Especially, almost all ectoparasitic wasps are idiobiont parasitoids.…”

“…Many superior species do not have a competition avoidance mechanism, while almost all-inferior species do (e.g., Leveque et al, 1993;Gauthier et al, 1999). In our situation, the endoparasitic, and competitive-inferior wasp D. sibirica shows competition avoidance of the sympatric ectoparasitic, and the competitive-superior species, D. isaea, but two ectoparasitic, and competitive-superior wasps, D. isaea and H. varicornis show no competition avoidance of D. sibirica.…”