Resource Partitioning among Parasitoids (Hymenoptera: Braconidae) of Phoracantha semipunctata in Their Native Range

o a h r f n C c H p a ( 1 r c d v f t v o p w i d The Eucalyptus longhorned borer, Phoracantha semipunctata (F.), is native to Australia, but it has been introduced without its natural enemies into many parts of the world in which its Eucalyptus spp. host has been planted. The beetle has developed large populations in these novel habitats and has been responsible for the mortality of large numbers of trees. Although there is a considerable catalogue of the parasitoids of the beetle in Australia, limited ecological information on the assemblage of parasitoids attacking P. semipunctata is available. We removed bark from 40 felled trees, recorded gallery width and bark thickness over parasitized larvae, and removed all parasitoids. Adult size, sex, and species were recorded when the parasitoid pupae eclosed. Syngaster lepidus Brullè, Jarra phoracantha Austin, Quicke, and Marsh, J. maculipennis Austin, Quicke, and Marsh, and J. painei Austin and Dangerfield were most commonly collected. The solitary parasitoid S. lepidus preferred maller larvae than did the gregarious Jarra spp. The wo species with shorter ovipositors, J. maculipennis nd J. painei, parasitized larvae under thinner bark han did the other two species with longer ovipositors. here was a significant positive correlation between ost larval size and number of parasitoid pupae of the regarious species. Also, there was a significant posiive correlation between host larval size and parasioid adult size. The ecological relationships between his assemblage of parasitoids and their beetle host ay be useful in establishing an effective biological ontrol program. © 2000 Academic Press