BEHAVIOR Evaluation of the Functional Response of Selected Arthropod Predators on Bollworm Eggs in the Laboratory and Effect of Temperature on Their Predation Efficiency M. N. PARAJULEE, 1,2 R. B. SHRESTHA, 1 J. F. LESER, 3 D. B. WESTER, 4 AND C. A. BLANCO 5 Environ. Entomol. 35(2): 379Ð386 (2006) ABSTRACT 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°C and the lowest numbers at 15°C; predation rate at 35°C was four times higher than that at 15°C. The prey densityÐ dependent behavior of predators and effect of temperature on their predation behavior are discussed. KEY WORDS functional response, attack rate, predation, cotton bollworm eggs, biological control THE COTTON BOLLWORM, Helicoverpa zea (Boddie), is a key pest of cotton in Texas and throughout the cotton belt (Parajulee et al. 1998, 2004, Williams 2004). Sev- eral studies have shown the potential of naturally occurring predator species in suppressing bollworm eggs and larval infestations in cotton (Ewing and Ivy 1943, Lingren et al. 1968, Ridgway and Lingren 1972, Bryson and Schuster 1975, McDaniel and Sterling 1979, Arnold 1999). However, the information on functional response and comparative ability of boll- worm predator species to consume the target pest is lacking. This information is critical to implementation of natural enemy conservation and augmentation of natural biological control. The information on labo- ratory functional response could be used to infer the basic mechanism of the predatorÐprey interactions in the Þeld (Houck and Strauss 1985). The number of prey that an individual predator kills is a function of prey density and is known as functional response (Holling 1966). Effectiveness of a predator is directly related to the type of their functional response. Arthropod predators display one of three typical functional responses, but the response may vary with crop phenology, habitat heterogeneity, age of preda- tor, and other biotic and abiotic factors. In a type 1 functional response, the number of prey killed in- creases linearly at a constant rate up to a maximum and remains constant as prey density further increases (combination of density-dependent and density-inde- pendent responses). The response is estimated by a linear equation N e =  + N [1] where N e = number of prey eaten, N = prey density (number of prey offered), and  and  = the intercept and slope of the prediction line, respectively. In a type 2 functional response, the number of prey killed approaches asymptote hyperbolically as prey density increases (declining proportion of prey killed or inverse density dependence). This type of response is estimated most commonly by a curvilinear function (Holling 1966), N e = aNT 1 + aNT h [2] where N e = number of prey eaten, a = the attack constant or instantaneous search rate, N = initial prey density, T = total available time, and T h = handling time (or the time taken by the predator to search, capture, consume, and digest one prey). In this model, 1 Texas Agricultural Experiment Station, 1102 E FM 1294, Lubbock, TX 79403. 2 Corresponding author, e-mail: m-parajulee@tamu.edu. 3 Texas Cooperative Extension, 1102 E FM 1294, Lubbock, TX 79403. 4 Texas Tech University, Department of Range, Wildlife, and Fish- eries, Box 2125, Lubbock, TX 79409. 5 USDAÐARS SIMRU, Stoneville, MS 38776. 0046-225X/06/0379Ð0386$04.00/0  2006 Entomological Society of America Downloaded from https://academic.oup.com/ee/article/35/2/379/377170 by guest on 30 July 2022