PROC. ENTOMOL. SOC. WASH. 105(4). 2003. pp. 970-981 AVIAN PREDATION ON IMMATURE STAGES OF THE LOCUST BORER, MEGACYLLENE ROBINIAE (FORSTER) (COLEOPTERA: CERAMBYCIDAE) James M. McCann and Dan M. Harman University of Maryland Center for Environmental Science, Appalachian Laboratory, 301 Braddock Road, Frostburg, MD 21532, U.S.A. (e-mail:
[email protected]); (JMM) present address: Maryland Department of Natural Resources. Wildlife Heritage Division, P.O. Box 68, Wye Mills. MD 21679. U.S.A. Abstract. — Avian predation t)n the locust borer, Megacyllene robiniae (Forster), was studied in 15 black locust (Robiiiia pseudoacacia Linnaeus) stands in western Maryland during 1987-88. Only woodpeckers were observed in the act of predation, but other avian species could not be discounted in assessment of past predation. The overall predation rate was low, ranging from just 0-1.7%, except in one stand where birds depredated 20% of the borers over a 2-year period. Birds focused their attacks on late instar larvae and pupae, the largest life stages. There was no evidence of predation on the much smaller, overwintering hrst instar larvae. Intensity of predation was related directly to larval and, especially, pupal density. Predation was more common in relatively small, unhealthy trees and in small trunks and branches. Most predation was attributed to hairy woodpeckers (Picoides villosits Linnaeus), based in part on direct observations and excavation char-acteristics. The overall low predation was likely due to a complex of factors that limited numerical and functional predatory responses to locust borers, including predator terri-torial behavior and seasonal shifts in foraging patterns, relatively low borer density, and black locust tree characteristics that could impede foraging (e.g., large thorns). Ke\ Words: black locust, excavations, tunnels, woodpeckers Woodpeckers have long been regarded as (Hanula and Fanzreb 1995). For pileated important predators of wood-borers (Beal woodpeckers {Dryocopits pileatus Linnae-191 1, Forbush 1927, Bent 1939), a complex us), studies of habitat preferences have in-of insects that tunnel in the sapwood and dicated importance of laige trees and snags heartwood of live trees and account for sub-(Renken and Wiggers 1993), whereas oth-stantial annual timber losses in the eastern ers have dealt with interspecific competition United States (Donley and Worley 1976, in which pileated woodpeckers enlarged Nielson 1981). Recent research has ad-nesting cavities of red-cockaded woodpeck-dressed biological aspects of potential ers (Saenz et al. 1998), and intra-speclfic wood-borer predators, particularly the red-competition between pileated woodpecker cockaded woodpecker (Picoides borealis males (Oberman 1995). Although consid-Vieillot). including foraging behavior erable research has been has been devoted (Engstrom and Sanders 1997, Doster and to the role of birds in regulating insect pop-James 1998). competition (Knapps 1997. ulations (e.g.. Knight 1958, Otvos 1965, Saenz et al. 1998). habitat (Engstrom and Dickson et al. 1979, Cooper and Smith Mikusinski 1998), and arthropod prey 1995), few studies have documented the
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