Abstract
In laboratory experiments host age had a significant effect on the parasitism of Papilio xuthus eggs attacked by three trichogrammatid parasitoids; Trichogramma papilionis NAGARKATTI, T. dendrolimi MATSUMURA and T. australicum GIRAULT. The host-age suitable for parasitism by these three parasitoids was limited within the first one-sixth of the host incubation period which was 96 hours at 25°C: nearly 100% of the host-eggs less than 12 hours old were parasitized, but the host-eggs more than 18 hours old were hardly parasitized. Dissection of the hosts attacked by T. papilionis and T. dendrolimi and observations on their oviposition behavior indicated that the reduction of parasitism on the older hosts occurs because these parasitoids refrain from oviposition after inserting their ovipositors into the hosts.
