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 Münchhausen (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 5.37 8.6% across pine bolts. Oak bolts yielded the braconid wasps (Hymenoptera: Braconidae) Wroughtonia ferruginea (Brues) and a species in the genus Atanycolus Förster (similar to Atanycolus charus (Riley)), and an ichneumonid (Hymenoptera: Ichneumonidae) in the genus Demopheles Förster. Pine bolts produced a braconid in the genus Digonogastra Viereck, and the tachinid fly (Diptera: Tachinidae) Billaea monohammi (Townsend). Résumé—Nous évaluons dans notre étude la relation entre la taille des billes provenant de chênes des marais, Quercus palustris Münchhausen (Fagaceae), et de pins blancs, Pinus strobus Linnaeus (Pinaceae), et le nombre et la taille corporelle des coléoptères cérambycidés (Coleoptera: Cerambycidae) qui s’y développent. Des billes de chêne, émergent des adultes de Graphisurus fasciatus (De Geer) (98% des coléoptères) et Xylotrechus colonus (Fabricius), alors que les billes de pin libèrent des Monochamus carolinensis (Olivier) (95%) et Astylopsis sexguttata (Say). Il y a une corrélation positive entre le nombre de G. fasciatus et le diamètre des billes de chêne, alors que le plus grand nombre des M. carolinensis émerge des billes de pin de diamètre intermédiaire. Il y a une corrélation positive entre la taille corporelle des deux espèces et le diamètre de la bille. Les taux de parasitisme sont très faibles, seulement 0.9% chez les chênes et en moyenne 5.37 8.6% dans l’ensemble des billes de pin. Les billes de chêne ont donné les bracons (Hymenoptera: Braconidae) Wroughtonia ferruginea (Brues) et une espèce du genre Atanycolus Förster (semblable à Atanycolus charus (Riley)), ainsi qu’un ichneumon (Hymenoptera: Ichneumonidae) du genre Demopheles Förster. Les billes de pin ont généré un bracon du genre Digonogastra Viereck et la mouche tachinide (Diptera: Tachinidae) Billaea monohammi (Townsend). Larvae of most species of cerambycid beetles feed subcortically in woody plants, and many species are important pests in managed and natural forests worldwide (Solomon 1995). For some cerambycid species, performance by the larvae is strongly influenced by the physical dimensions of larval hosts (Hanks et al. 2005), as well as parasitism rate (Hanks et al. 2001). Here, we summarise research that assessed the relationship between the size of bolts cut from trees and the number and size of cerambycid beetles that emerge, and parasitism rates. The study was conducted in a , 0.08 ha tree plantation (United States of America: Illinois: Champaign Co.; 40805006.4300N, 88812049.8800W) with pin oaks, Quercus palustris Münchhausen P.F. Reagel, L.M. Hanks, Department of Entomology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States of America M.T. Smith, USDA-ARS Beneficial Insects Introduction Research Lab, Newark, Delaware 19713, United States of America Corresponding author (e-mail: [email protected]). doi:10.4039/tce.2012.39 Received 7 March 2011. Accepted 7 July 2011. Can. Entomol. 144: 1–4 (2012) 2012 Entomological Society of Canada 1