Feeding Specialization in Predatory Insects: Hunting and Attack Behavior of Two Stinkbug Species (Hemiptera: Pentatomidae)

Two species of predatory stinkbugs (Hemiptera: Pentatomidae) that reproduce in stands of goldenrod (Solidago spp.) near Ithaca, New York, were observed as they hunted for and attacked prey on goldenrods. One species, Perillus circumcinctus, is a specialist predator of Chrysomelid beetles while the other species, Podisus maculiventris, is a generalist predator which feeds on many kinds of prey. Nymphs of both species mature in goldenrod stands by feeding upon beetles of the genus Trirhabda (Chrysomelidae). Nymphs of both predators used similar tactics (e.g., searching velocities, sites searched) when hunting on goldenrods. Although nymphs of P. circumcinctus took much less time to subdue Trirhabda larvae than nymphs of P. maculiventris, nymphs of both species generally succeeded ultimately in overcoming these prey. In contrast, nymphs of both species failed in most attacks on Trirhabda adults and other potential prey which inhabit goldenrod stands. It is concluded that more effective exploitation of Trirhabda beetles by the specialist predator compared to the generalist derives primarily from differences in their timing of reproduction rather than from differences in hunting and attack behavior. INTRODUCTION Feeding specialization in insects has long been, and continues to be, a subject of major interest (e.g., Brues, 1946; Feeny, 1975; Hassell and Southwood, 1978; Fox and Morrow, 1981). A prevailing view is that by specializing, species come to harvest their preferred foods more effectively than species with more generalized habits (e.g., MacArthur, 1972). It remains unclear, however, how generally this hypothesis applies in nature (Fox and Morrow, 1981). I have tested this hypothesis by comparing the habits of two predatory stinkbugs [Podisus maculiventris (Say) and Perillus circumcinctus Stal; Hemiptera: Pentatomidae]. Podisus maculiventris occurs throughout North America and has very broad feeding habits, foraging in a wide variety of habitats and attacking many types of prey. Mukerji and LeRoux (1965), for example, list over 50 species of prey belonging to 33 families and eight orders. My observations near Ithaca, New York, confirm the diversity of habitats frequented and prey consumed by this predator at a single geographical locality (Evans, 1980). Perillus circumcinctus, in contrast, has much narrower feeding habits; occurring in northeastern North America, it has been recorded from only a few habitats where it preys upon larvae of chrysomelid beetles which feed externally upon leaves (Evans, 1980). Because P. circumcinctus is far more restricted in its feeding habits than P. maculiventris, I consider the former species a feeding "specialist" (on chrysomelid beetles) and the latter species a "generalist" (that feeds in nature on many types of prey, including chrysomelid beetles). Both predators occur and reproduce in the dense stands of goldenrod (Solidago spp.) that colonize old fields and other open sites near Ithaca. Nymphs of both species mature by feeding upon beetles of the genus Trirhabda (Chrysomelidae). Specialization by Perillus circumcinctus is reflected in that reproduction by this predator is synchronized with that of the univoltine Trirhabda so that nymphs develop almost entirely on a diet of beetle larvae. In contrast, nymphs of Podisus maculiventris appear a few weeks later and thus complete later instars by feeding on beetle adults (Evans, 1982a). 'Present address: Division of Biology, Kansas State University, Manhattan 66506.