Historically considered innocuous, red oak borer, Enapholodes rufulus (Haldeman), is currently experiencing an outbreak of epidemic proportions in the Ozark National Forest of Arkansas, which is resulting in widespread tree mortality. The cause of this outbreak is currently unknown. Insect populations increase when they escape natural controls, e.g. limited food resources, predators, etc. Woodpeckers and nitidulids have accounted for some larval mortality but the majority of mortality is from unknown factors. Larvae of E. rufulus feed in the phloem of living oak trees so phloem sandwiches were used to observe inter- and intra-specific predation of E. rufulus. Our investigations reveal that E. rufulus is cannibalistic. One of the potential benefits of this behavior, weight gain, is examined. Observations are also made on the contribution to larval mortality of some intraguild insects, e.g. nitidulid and elaterid larvae. This research has important implications in red oak borer population dynamics and may potentially help to explain the recent shift in population levels.