Evaluation of the Functional Response of Selected Arthropod Predators on Bollworm Eggs in the Laboratory and Effect of Temperature on Their Predation Efficiency

A functional response study of the eight most common arthropod predators of cotton bollworm, Helicoverpa zea (Boddie), eggs was conducted in the laboratory. Predators were starved for 24 h, and single predators were exposed to different prey density treatments. Predation response was observed at 6, 12, and 24 h after feeding trials began. At the highest prey density (150 eggs per predator), Hippodamia convergens Guerin-Meneville and Collops quadrimaculatus (F.) adults and Chrysopa oculata Say larvae showed the highest consumption rates (116, 85, and 119 eggs/24 h, respectively), followed by H. convergens larvae (51 eggs/24 h), adult Geocoris punctipes (Say) (45 eggs/24 h), and adult Scymnus loewii Mulsant, Orius insidiosus (Say), Notoxus spp., and Nabis capsiformis Germar (1, 1, 10, and 12 eggs/24 h, respectively). Adult Notoxus spp., N. capsiformis, and O. insidiosus showed type 1 functional response, whereas adult C. quadrimaculatus, G. punctipes, H. convergens, and larval H. convergens and C. oculata showed type 2 response. All predators consumed the highest number of bollworm eggs at 35 degree C and the lowest numbers at 15 degree C; predation rate at 35 degree C was four times higher than that at 15 degree C. The prey density-dependent behavior of predators and effect of temperature on their predation behavior are discussed.