Timing of Reproduction by Predatory Stinkbugs (Hemiptera: Pentatomidae): Patterns and Consequences for a Generalist and a Specialist

Abstract

The seasonal timing of reproduction was examined for two predatory stinkbugs (Hemiptera: Pentatomidae) in stands of goldenrod (Solidago spp.) near Ithaca, New York, USA. One species, Perillus circumcinctus, is a specialist predator of soft—bodied beetle larvae and occurs in few habitats. The second species, Podisus maculiventris, is a generalist predator that attacks many kinds of insect prey in a great diversity of habitats. In goldenrod stands both predators fed primarily on Trirhabda spp. (Coleoptera: Chrysomelidae). Sweep samples revealed that nymphs of the specialist predator matured in synchrony with larvae of the univoltine Trirhabda in May and June. Most nymphs of the generalist predator matured several weeks later and older instars of this predator fed primarily on Trirhabda adults. Nymphs of both predators easily overpower larvae of Trirhabda, but they rarely succeed in capturing the alert beetle adults; consequently the availability of food in goldenrod stands deteriorates as the beetles mature. Field patterns of body size of the predators reflect the seasonal change in food supply. For both predators, adult body size depends upon the rate at which nymphs consume prey. As the season progressed, the size of newly molted adults of both stinkbugs declined, paralleling the earlier decline in availability of Trirhabda larvae as prey for nymphs. Because of differences in seasonal appearance, most specialist predators attained adult sizes in the field approximating the maxima attained in the laboratory, while most generalist predators attained significantly smaller sizes. Those few generalist predators that did mature early also generally attained maximum size; they experienced little difficulty finding, capturing, and digesting Trirhabda larvae. These results indicate that the specialist predator exploits Trirhabda populations more effectively that the generalist. The key difference in the habits of the two predators lies not in the foraging efficiency of nymphs nor in biochemical adaptation to the prey, but rather in timing of reproduction. Well—timed oviposition in goldenrod stands by specialist females ensures that offspring mature during the short period each summer when prey are easily harvested. In contrast, the relatively poor timing of oviposition by generalist females results in most of their offspring experiencing substantial food stress.