Relative Prey Weight Influences Handling Time and Biomass Extraction in Sinea confusa and Zelus renardii (Heteroptera: Reduviidae)

Abstract

The influence of relative predator-prey weight ratios in feeding behavior was investigated in females of 2 species of reduviids, Sinea confusa Caudell and Zelus renardii Kolenati. Using 10-140 mg moth larvae, Heliothis virescens (F.) as prey (presented in 7 weight groups), we measured handling time and extracted biomass of prey over a wide range of predator-prey weight ratios (0.3-4.5:1). Handling time decreased exponentially and extracted biomass increased linearly as predator-prey weight ratios increased. At predator-prey ratios that were ≈1:1, handling time was ≈100 min for both species. Extracted biomass increased linearly with increases in prey weight, but these increases were not proportional to either increases in prey weights or handling times concomitant with increasing prey weights. Rate of consumption averaged ≈110 μg/min for both species. Relative consumption rate was significantly higher for S. confusa than it was for Z. renardii. We propose the concept of the major investor strategy for predators that can use extra-oral digestion to utilize relatively large prey. Major investors, as seen here, invest large amounts of time and materials in each large prey item, and they must, in turn, extract a substantial nutrient reward from each prey before abandoning it to attack a new prey. Therefore, with large prey, major investors would not conform to functional response kinetics.