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Performance of an insect predator while attacking external and internal stages of an endophytic herbivore.
Aukema, Brian1, Raffa, Kenneth1, 1
ABSTRACT- One advantage that has been proposed to an endophytic life history strategy is predator avoidance. Predators of endophytic insects must not only find suitable prey habitat, but also handle prey in a resource-limited environment. We evaluated some of the constraints on a predator of bark beetles (Coleoptera: Scolytidae). We selected a predator, Thanasimus dubius (Coleoptera: Cleridae), that preys both on Ips pini adults on the bark surface and on larvae within the host tree. We varied prey and predator densities during both phases of predation, in laboratory experiments. T. dubius adults showed a strong functional response to adult pine engravers on the surface of red pine logs. The ratio dependent slope of per capita predation was 0.341. However the functional response of T. dubius larvae feeding on I. pini larvae within the plant was less defined. This was likely due to cannibalism and the complex architecture of prey galleries. Emergence of adult predator progeny was usually less than 0.1 beetles per prey ovipositional gallery. Increased densities of T. dubius on the plant surface reduced the per capita prey capture through interference. Within the plant, either crowding by T. dubius or low herbivore densities reduced the emergence of adult predator progeny. We quantify a narrow window of predator and prey densities that can generate successful reproduction, i.e. replacement rates greater than 1, for this predator that specializes on endophytic herbivores.
KEY WORDS: Thanasimus dubius, Ips pini, predation, endophytes