INTERSPECIFIC COMPETITION BETWEEN EUPELMUS-VUILLETI AND DINARMUS-BASALIS, 2 SOLITARY ECTOPARASITOIDS OF BRUCHIDAE LARVAE AND PUPAE

Coexistence of two solitary ectoparasitoids of bruchids may be the res ult of counter-balanced competition. Some strategies in interspecific competition at the extrinsic level of female behaviour are identified. Dinarmus basalis (Rondani) (Hymenoptera; Pteromalidae) has adapted an evasion strategy to avoid competition. Females of D. basalis show int erspecific discrimination against hosts parasitized by Eupelmus vuille ti Crawford (Hymenoptera; Eupelmidae) and lay fewer eggs in the presen ce of females or hosts parasitized by the latter. Eupelmus vuilleti ha s adapted an aggressive strategy. In contrast to D. basalis, E. vuille ti concentrates her ovipositions on hosts already parasitized by D. ba salis. Females of E. vuilleti preferably use oviposition holes made by other parasitoids, and are able to kill eggs and larvae of D. basalis selectively by thrusts of their ovipositor (ovicide and larvicide). F urthermore, E. vuilleti can act as a facultative hyperparasitoid on ol der larvae of D. basalis. The number of E. vuilleti offspring is not a ffected by the presence of D. basalis on a host. Our study does not pr ovide insight in the process of larval competition.