The little-known borers: Life history studies of native horned powderpost beetles (Bostrichidae) in the Midwest

Despite a worldwide distribution, common interception at ports and a role in carbon cycling and other ecological processes, wood boring beetles in the family Bostrichidae are little studied outside two largely tropical and exotic stored grain pests Rhyzopertha dominica and Prostephanus truncates. Basic life history information related to native habitat associations, phenology, and host use are thus lacking for most species. Here we report results of a 3-year study investigating these characteristics for native Bostrichids found in Northern Illinois using ethanol traps and host choice assays. The three most common species captured were Amphicerus bicaudatus, Scobicia bidentata, and Xylobiops basilaris. Abundance varied greatly between years, but beetles were consistently more abundant in endangered oak savanna than in nearby woodland ecosystems. Spring flight activity differed among species, possibly due to differences in overwintering strategies, with female A. bicaudatus flight occurring when temperatures rose above 18°C and S. bidentata and X. basilaris flight occurring later in the spring after further heat accumulation and development. In host use assays, which included all 7 common woody plants found in the oak savanna, both A. bicaudatus and S. bidentata showed a strong attraction and feeding preference for oak twigs (Quercus velutina). X. basilaris numbers were too low to conduct similar experiments. These results provide some of the first indications of habitat and host preferences in native North American Bostrichids and provide a framework for future study of this common yet understudied beetle family.