The chemical ecology of host foraging, aggregation, and prophylactic microbial defense in the western boxelder bug, Boisea rubrolineata (Barber) (Heteroptera: Rhopalidae)

The boxelder bug (BEB), Boisea rubrolineata (Heteroptera: Rhopalidae), is a specialist herbivore of boxelder trees, Acer negundo. BEBs form spectacular aggregations on (i) pistillate A. negundo when seeds are maturing, (ii) in and around shelters in fall and winter, and (iii) in response to warm sunlight. When sunbathing, BEBs release from their posterior dorsal abdominal gland an odorous blend of monoterpenes with heretofore unknown biological function. We reveal that (1) BEBs exploit semiochemicals (phenylacetonitrile, 2-phenethyl acetate) from host trees to locate them during foraging and colonization, (2) aggregation and sexual communication of BEBs are mediated by a complex pheromone system, and (3) BEBs in warm sunlight, but not in shade, exude and spread copious amounts of monoterpenes onto their cuticle. These monoterpenes do not serve as a pheromone, but rather a means of sanitation that interferes with spore germination and growth of the pathogenic fungus Beauvaria bassiana.