Predacious hister beetles (Coleoptera: Histeridae) commonly found associated with Ips engraver beetles (Coleoptera: Scolytidae) under the bark of pine trees in Louisiana include species in the Cylistix (Platysoma) and Plegaderus genera. We designed this study to evaluate seasonal abundance, emergence, and host finding mechanisms in histerid predators of Ips beetles as a precursor to evaluating their potential use as biological control agents. Data from flight traps demonstrated that histerid seasonal abundance mimicked Ips activity. Hister beetles arrived at Ips-infested logs beginning one week after initial Ips attacks. Cylistix parallela (Say) and Cylistix sp. emerged from logs in a bimodal pattern, with the first peak occurring during the Ips emergence period and the second peak four weeks later, indicating that these histerids feed on both bark beetles and organisms arriving later in the colonization sequence. Histerids likely use both visual and chemical cues to locate prey habitats. Both Cylistix attenuata (LeConte) and Cylistix cylindrica Paykull arrived at vertically positioned logs in significantly higher numbers than at horizontal logs, while C. parallela significantly were more abundant at horizontally positioned logs. These data support the hypothesis that some histerids visually orient toward Ips-infested pine logs, which are often blown-down or cut trees, while other hister beetles may visually orient toward standing pines, such as those attacked by the southern pine beetle, Dendroctonus frontalis Zimmermann. Y-tube olfactometer assays revealed differential attraction of C. parallela and Plegaderus transversus Say to Ips pheromones.
Species 1: Coleoptera Histeridae Cylistix
Species 2: Coleoptera Histeridae Plegaderus
Species 3: Coleoptera Scolytidae Ips
Keywords: predators, bark beetles
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