Trade-Offs in Body Weights, Egg Loads, and Fat Reserves of Field-Collected Podisus maculiventris (Heteroptera: Pentatomidae)

Abstract

The spined soldier bug, Podisus maculiventris (Say), was collected in 8 field sites in Indiana during the summers of 1987-1989. The insects were collected using both pheromone traps and sweep nets. Insect weights were recorded for all 3 yrs, and egg loads and lipid content in the fat body were recorded for 1988 and 1989. Analysis of the weights revealed that females were heavier than males. Female body weight, egg load, and lipid content were compared against corresponding measurements of predators subjected to different prey regimens in the laboratory. These comparisons indicate that field populations often had measurements similar to predators provided 1 prey item every 3-9 d. Predators collected during the summer of 1988 revealed higher mean lipid content, smaller egg loads, and lower weights than those collected in 1989. These traits, together with the relative scarcity of predators found in 1988, suggest that the predators were responding to greater food stress by conserving energy reserves in the fat body and diverting them away from reproduction. We discuss possible implications of these observations.