Chemically mediated predator-free space: Herbivores can synergize intraspecific communication without increasing risk of predation

Natural enemies of herbivores often locate cryptic insects by responding to volatiles associated with the prey's feeding and mating. For example, pred ators of bark beetles (Coleoptera: Scolytidae) exploit the aggregation pher omones that their prey use to attract mates and secure hosts. Bark beetles are cryptic insects that feed and develop in the subcortical tissues of tre es and spend all but a portion of their life history within this habitat. T he pine engraver, Tps pini, produces the pheromone ipsdienol throughout its transcontinental range. Predators of I. pini exploit this chemical as a ka iromonal cue. Eastern and Midwestern I. pini populations also produce lanie rone, which synergizes their attraction to ipsdienol. We evaluated the effe cts of varying amounts of lanierone, in combination with a constant amount of racemic ipsdienol, on the relative attraction of I. pini and its major p redators in Wisconsin. Higher numbers of I. pini were captured with increas ing release rates of lanierone. In contrast, the numbers of the major preda tors, such as Thanasimus dubius. Enoclerus nigrifrons, Platysoma cylindrica , and P. parallelum, did not differ among different lanierone release rates . The response of I. pini but not their predators to lanierone at ecologica lly realistic release rates may be part of a coevolving interaction between predators and prey and offers new strategies for semiochemically based pes t management by selectively removing pests and leaving predators.