Host discrimination ability in the tephritid parasitoid Psyttalia concolor (Hymenoptera: Braconidae)

Psyttalia concolor (Szépligeti) (Hymenoptera: Braconidae) is a koinobiont larval-pupal endoparasitoid of many Tephritidae of economic importance. Little has been reported on the ability of females to discriminate between healthy and parasitized hosts, as well as parasitized versus superparasitized larvae. Two-choice bioassays were conducted to evaluate the preferences of P. concolor naïve females for healthy or single-parasitized/superparasitized C. capitata larvae, as well as the host discrimination ability among medfly larvae which had been superparasitized by the same wasp or by a conspecific one. Psyttalia concolor preferred to oviposit in a unparasitized C. capitata larva than in a self-parasitized one. Females also showed an innate ability to discriminate between larvae parasitized twice or only once, preferring the latter. This ability helps the female to optimise its oviposition decisions by deliberately avoiding superparasitized hosts, since it is known that they give a lower return in offspring number and quality than do singly parasitized hosts. Our findings contribute to a better knowledge of the P. concolor host location behaviour and also to improve its mass-rearing technique through a rational management of the host/parasitoid ratio and the host exposure time. Indeed, the proper setting of these parameters allows to reduce the fraction of single-parasitized and heavily superparasitized larvae and to enhance P. concolor rearing in terms of parasitoid offspring.