Seasonal Abundance, Arrival and Emergence Patterns of Predaceous Hister Beetles (Coleoptera: Histeridae) Associated with Ips Engraver Beetles (Coleoptera: Scolytidae) in Louisiana

The most common predaceous hister beetles (Coleoptera: Histeridae) found associated with Ips engraver beetles (Coleoptera: Scolytidae) in southern Louisiana were Platysoma attenuata LeConte, P. cylindrica (Paykull), P. parallelum (Say), and Plegaderus transversus (Say). The seasonal abundance of histerids caught in flight traps coincided with Ips spp. activity in the area. Histerid adults were initially caught in sticky traps on Ips-infested loblolly pine logs 1 wk after Ips spp. attacks had begun. As a group, histerids emerged from logs in a bimodal pattern with the first peak occurring during Ips spp. emergence and a second 4 wks later. The abundance of P. parallelum and P. transversus indicates that they likely fed on bark beetles and organisms arriving later in the colonization sequence. Visual orientation appeared to play a role in attraction of histerids to logs colonized by bark beetles. Platysoma attenuata preferred vertically-positioned logs to horizontal logs, while P. parallelum was the opposite. These results suggest that some histerids may be visually attracted to horizontal silhouettes, such as pine trees that have been blown down or felled and often are infested by Ips spp. Other hister beetles may prefer vertical silhouettes, such as standing pines, which tend to be colonized by the southern pine beetle, Dendroctonus frontalis Zimmermann.