Host species preference and larval performance in the wood-boring beetlePhoracantha semipunctata F

Adults of the wood-boring beetlePhoracantha semipunctata F. showed variability in their attractiveness to five varieties ofEucalyptus when presented with an array of logs in a natural setting. Logs of two host varieties (E. camaldulensis Dehnhardt and the hybridE. trabutii) attracted two to three times more adult beetles than did logs of other host species (E. cladocalyx F.,E. grandis Hill ex Maiden andE. tereticornis Small). In the field, high oviposition rates byP. semipunctata adults resulted in severe competition among larvae. Larval survivorship was low in field logs ofE. trabutii and high inE. cladocalyx logs, although these hosts were the most and least attractive to the adult beetles, respectively. However, when logs were hand infested at low larval densities, survivorship ofP. semipunctata larvae was highest in logs of bothE. camaldulensis andE. trabutii. These findings suggest that adult beetles in the field were most attracted to those logs ofEucalyptus species that represented the highest quality hosts for their progeny under conditions of reduced larval competition.