The bark beetle Ips pini (Coleoptera: Scolytidae) is a chronic pest of pine forests throughout North America. Pioneering males bore into the subcortical region of a tree and emit aggregation pheromones, which attract both male and female conspecifics. Females join established males under the bark, while arriving males excavate additional nuptial chambers. Predators exploit these pheromones as kairomones and arrive almost simultaneously. The most abundant predator in Wisconsin, Thanasimus dubius (Coleoptera: Cleridae), preys on adult bark beetles on the surface of the tree. We conducted a laboratory assay to study the predation of T. dubius on male and female I. pini arriving at a simulated tree under attack. Predation on females was less than that of males, presumably because females can rapidly enter nuptial chambers previously excavated by males. Predation on female I. pini increased with increasing numbers of T. dubius. Arriving male I. pini suffered high mortality when T. dubius were present, independent of the number of females when males were already established under the bark. Males that arrived later in the colonization sequence experienced higher predation than pioneering males. The presence of females with late-arriving males did not confer a survival advantage on those males. These data show that T. dubius can negatively impact the number of successful colonizing bark beetles arriving at a host under attack and that predation varies with gender and arrival sequence.
Species 1: Coleoptera Scolytidae Ips pini (pine engraver)
Species 2: Coleoptera Cleridae Thanasimus dubius (checkered beetle)
Keywords: predation, bark beetles
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