HOST SPECIES PREFERENCE AND LARVAL PERFORMANCE IN THE WOOD-BORING BEETLE PHORACANTHA-SEMIPUNCTATA F

Adults of the wood-boring beetle Phoracantha semipunctata F. showed va riability in their attractiveness to five varieties of Eucalyptus when presented with an array of logs in a natural setting. Logs of two hos t varieties (E. camaldulensis Dehnhardt and the hybrid E. trabutii) at tracted two to three times more adult beetles than did logs of other h ost species (E. cladocalyx F., E. grandis Hill ex Maiden and E. tereti cornis Small). In the field, high oviposition rates by P. semipunctata adults resulted in severe competition among larvae. Larval survivorsh ip was low in field logs of E. trabutii and high in E. cladocalyx logs , although these hosts were the most and least attractive to the adult beetles, respectively. However, when logs were hand infested at low l arval densities, survivorship of P. semipunctata larvae was highest in logs of both E. camaldulensis and E. trabutii. These findings suggest that adult beetles in the field were most attracted to those logs of Eucalyptus species that represented the highest quality hosts for thei r progeny under conditions of reduced larval competition.