Feeding responses of hemipteran predators to Spissistilus festinus (Homoptera: Membracidae)

The developmental stages of Spissistilus festinus (Say) most susceptible to predation by Geocoris punctipes (Say) and Nabis roseipennis Reuter female adults, and Orius insidiosus (Say) of undetermined sex were determined. A single starved predator was placed during 24h with each of five nymphal and adult S. festinus stages in a caged soybean plant. Highest prey mortality (90-100%) with G. punctipes was obtained with early nymphal stages. Nabis roseipennis attacked all nymphal stages equally well. Orius insidiosus did not feed on S. festinus.; Feeding preference of G. punctipes and N. roseipennis female adults was studied in the growth chamber. Spissistilus festinus mortality due to predators did not decrease when Pseudoplusia includens (Walker) and/or Helicoverpa zea (Boddie) larvae were available as alternative prey. Both predators consumed from 33 to 100% of the nymphs even in the presence of lepidopteran larvae. Feeding response of the predators to different S. festinus and P. includens density combinations also was studied. There was not a real preference for either prey species by either predator.; A G. punctipes laboratory gender study indicated no significant difference in percent S. festinus nymphal mortality by either sex.; A field study to determine feeding response of G. punctipes and N. roseipennis to different S. festinus densities at three soybean searching area sizes also was conducted. Increasing searching areas resulted in a decline of the percent S. festinus nymphal mortality during 1992. Results in 1993 were not consistent. Prey density had a significant effect on prey mortality during 1993. Highest predation mortality (39.8%) occurred at the six prey density level. Data obtained indicate that G. punctipes and N. roseipennis contribute to reduction in number of S. festinus nymphs in soybean.