SELECTIVE HOST-FEEDING ON PARASITIZED HOSTS BY THE PARASITOID ITOPLECTIS-NARANYAE (HYMENOPTERA, ICHNEUMONIDAE) AND ITS IMPLICATION FOR BIOLOGICAL-CONTROL

Host-feeding by parasitoid wasps has been viewed as a positive attribu te for biological control, because hosts are killed as a result of hos t-feeding in addition to parasitism. Host acceptance and host-feeding responses to unparasitized vs. conspecifically parasitized hosts by th e parasitoid wasp Itoplectis naranyae Ashmead were studied in the labo ratory. Female I. naranyae selected to oviposit in unparasitized hosts and those that had been parasitized Ih previously, in equal proportio ns, even when allowed access to both types of host. Females also fed u pon both types of host equally. Females, however, avoided ovipositing in hosts parasitized 40 h and 70 h previously, and preferentially fed upon them when allowed access both to parasitized and to unparasitized hosts. Parasitoid progeny in hosts which had been used for host-feedi ng suffered a high degree of mortality. Females used host internal cha nges as cues for deciding whether to feed on hosts. It is suggested th at immature parasitoid mortality can be increased due to female prefer ence for using parasitized hosts for host-feeding. Hence, host-feeding by I. naranyae may not be an advantageous biological control characte ristic. The adaptive significance of selective host-feeding is also di scussed.