PATCH CHOICE IN THE ANTHOPHILOUS AMBUSH PREDATOR PHYMATA-AMERICANA - IMPROVEMENT BY SWITCHING HUNTING SITES AS PART OF THE INITIAL CHOICE

Optimal foraging theory predicts that foragers with an imperfect knowl edge of the environment will invest time sampling the foraging area. T he ambush bug Phymata americana Melin appertains to this category of f oragers because it has shown, in previous studies, apparently nonoptim al behaviour in choosing patches while crawling on the ground. Even so . we hypothesize that, atop the canopy where they normally seek prey, they can easily switch to a better position. To examine this hypothesi s and to test the prediction of optimal foraging theory. adult male an d female ambush bugs were released in an experimental arena containing six different kinds of patches of Solidago canadensis: (1) normal, le afy stems with inflorescences, (2) bare stems without inflorescences. (3) leafy but deflowered stems, (4) normal stems with ambush bugs of t he opposite sex in the inflorescences, (5) normal stems with dead hous e flies (Musca domestica) (prey) hanging over the flower, and (6) norm al stems with dead honeybees (Apis mellifera) (prey) hanging over the flower. The bugs showed only weak discrimination in choosing a stem fr om the ground. However, once atop the canopy (stems or inflorescences) , the bugs switched quickly to other patches, significantly improving their situation. These results suggest that this ambush predator has s ome ability to recognize not only vegetation and floral cues, but also the presence of other insects in flowers, i.e., prey and the opposite sex. Sexual diethism is also indicated.