Predatory interactions within a guild of predaceous heteroptera common in soybean, and their effect on survival of a soybean pest

Nabis roseipennis Reuter (damsel bug), Geocoris punctipes (Say) (bigeyed bug) and Orius insidiosus (Say) (insidious flower bug) are common and important predators in soybean agroecosystems. These heteropterans coexist phenologically and spatially in soybean, and form a predator guild that feeds on similar resources in a similar manner. However, these species are generalist predators and so may prey upon each other. Predatory interactions such as cannibalism and intraguild predation (IGP) among guild members can affect their impact on prey species, many of which are pests in soybean (e.g., corn earworm). These interactions were examined with different age-class, gender, and species combinations in simple and complex enclosures in a laboratory setting.; N. roseipennis was the most cannibalistic species and O. insidiosus the least. G. punctipes demonstrated the highest rate if IG predation. Gender did not significantly affect propensity for cannibalism or IGP for any species. Cannibalism and IGP were high when predators differed in size, with the larger preying on the smaller in nearly all predatory encounters. When predators were similar in size, IGP was lower and cannibalism much lower. Both cannibalism and IGP decreased in enclosures with more complex architecture, and also decreased in the presence of extraguild prey.; When N. roseipennis and G. punctipes were tested to examine the effect of predator interactions on prey consumption (of corn earworm eggs), strong interference effects were seen for nabids in cannibalism experiments and for the two species together in IGP experiments.; Predator location was also noted on young soybean plants. Predators placed alone on soybean largely segregated themselves onto different specific plant sites based on species, and within species there were age-class-specific differences in site preference. When food (in the form of corn earworm eggs) was placed on soybean plants, predators tended to prefer the location with eggs to previous site preferences.; Ground activity over three field seasons was examined for the guild predators using suction sampling and pitfall traps in soybean fields. Despite reports in the literature describing G. punctipes as a ground-dwelling predator, bigeyed bugs were primarily foliage inhabitants in Kentucky soybean fields. N. roseipennis was found on the ground more often than the other guild species, and O. insidiosus was rarely collected on the ground. Younger nabid instars were captured in disproportionate numbers relative to abundance in the fields, indicating that nymphs were ground active to a greater extent than adults. Diel cycle of ground activity was examined, and nabids were found to be active for the 24-hr cycle, but mostly during the nocturnal hours, while geocorids were active almost exclusively during the day.