Host egg kairomones essential for egg-larval parasitoid,Ascogaster reticulatus watanabe (Hymenoptera: Braconidae) : I. Internal and external kairomones.

An artificial egg with a Parafilm membrane was devised for the oviposition ofAscogaster reticulatus Watanabe (Hymenoptera: Braconidae), an egg-larval parasitoid of the smaller tea tortrix,Adoxophyes sp. (Lepidoptera: Tortricidae). Both external and internal kairomones were essential. The external kairomone, needed for host location and acceptance, was extracted with 70% ethanol, and the internal kairomone, needed for oviposition, was extracted with water. Female parasitoids responded to the external kairomone and oviposited through the membrane into the artificial egg when the supernatant of host egg-mass homogenate was inside, whereas they did not when water or saline solutions were inside. Thus an internal kairomone is responsible for the oviposition in the host egg. The internal kairomone apparently was not specific for the host egg mass because oviposition activity was found not only in egg, larval, and pupal stages of the host, but also in larvae of other species of Lepidoptera and Coleoptera.