Effects of larval host diameter on body size, adult density, and parasitism of cerambycid beetles

In this study, we assessed the relationship between the size of bolts cut from pin oak trees, Quercus palustris Munchhausen (Fagaceae), and eastern white pines, Pinus strobus Linnaeus (Pinaceae), and the number and body size of cerambycid beetles (Coleoptera: Cerambycidae) that develop within them. From oak bolts emerged adult Graphisurus fasciatus (De Geer) (98% of beetles) and Xylotrechus colonus (Fabricius), while pine bolts produced Monochamus carolinensis (Olivier) (95%) and Astylopsis sexguttata (Say). The number of G. fasciatus was positively correlated with the diameter of the oak bolts, while the greatest number of M. carolinensis emerged from pine bolts of intermediate diameter. Body size of both species was positively correlated with bolt diameter. Rates of parasitism were very low, only 0.9% for oaks, and averaging 5.3 +/- 8.6% across pine bolts. Oak bolts yielded the braconid wasps (Hymenoptera: Braconidae) Wroughtonia ferruginea (Brues) and a species in the genus Atanycolus Forster (similar to Atanycolus charus (Riley)), and an ichneumonid (Hymenoptera: Ichneumonidae) in the genus Demopheles Forster. Pine bolts produced a braconid in the genus Digonogastra Viereck, and the tachinid fly (Diptera: Tachinidae) Billaea monohammi (Townsend).