Facultative intraguild predation of red oak borer larvae (Coleoptera: Cerambycidae)

In the Ozark National forests of Arkansas and Missouri, all outbreak of a native cerambycid beetle, the red oak borer, Enaphalodes rufulus (Haldeman), seems responsible for widespread oak mortality. The underlying reasons for this outbreak are being studied. Historically, a small portion of within-tree red oak borer mortality has been attributed to natural enemies (woodpeckers and nitidulid larvae), but the majority of mortality is from unknown factors. In four experiments, phloem sandwiches were used to observe inter- and intraspecific predation on red oak borer larvae. Our studies revealed that red oak borer was cannibalistic and that this behavior resulted in statistically significant weight gain. Observations were also made on predaceous behavior by associated insect larvae, specifically carpenterworms, elaterids, and nitidulids. We found that carpenterworms and elaterids will eat red oak borer larvae, but nitidulids exhibited no predaceous behavior. These observed behaviors may have important implications for red oak borer population dynamics because they identify potential mortality factors to red oak borer larvae.