Specialized predation on plataspid heteropterans in a coccinellid beetle: adaptive behavior and responses of prey attended or not by ants

Two plataspid hemipteran species proliferated on Bridelia micrantha (Euphorbiaceae). Colonies of Libyaspis sp., never attended by ants, developed on branches, while Caternaultiella rugosa lived at the base of the trunks, mostly in association with Camponotus brutus that attends them in carton shelters. Both plataspid species are prey of the coccinellid beetle Anisolemnia tetrasticta, whose larvae always detected them by contact. When attacked the Libyaspis nymphs cowered, so that the hypertrophied lateral sides of their tergits made contact with the substrate, but the ladybirds slid their long forelegs under these nymphs, lifted them, and bit them on the ventral face. The Caternaultiella nymphs, which do not have hypertrophied extremities of the tergits, tried to escape at contact with the ladybirds, but were rarely successful. To capture them, the ladybirds either adopted the previous behavior or directly grasped then bit them. We noted a graded aggressiveness in the ants toward the ladybirds according to the situation: no aggressiveness on the tree branches; stopping the ladybirds that approached the shelters where the ants attended Caternaultiella; and full attack of ladybirds that tried to capture Caternaultiella nymphs situated outside shelters. The latter behavior can emit an alarm pheromone that triggers the dispersion of their congeners while attracting attending C. brutus workers. Naive workers are not attracted, so we deduce that this behavior is the result of a kind of learning. Copyright 2002.