Size-specific provisioning by Cicada killers, Sphecius speciosus, (Hymenoptera: Crabronidae) in North Florida

Abstract

Eastern cicada killer wasps (Sphecius speciosus Drury) mass-provision underground nest burrows with cicadas they capture and paralyze in nearby trees. We studied provisioning by female cicada killers at 2 aggregations in north Florida where a variety of cicada species, with a large range in body size, are used as prey. We captured and measured samples of male and female wasps and we uniquely marked samples of females. We measured and identified paralyzed cicadas that we retrieved from females as they were provisioning their nests. We compared the body sizes of male and female wasps, and cicada prey, between locations. The mean body sizes of male wasps, female wasps, and cicadas from the St. Johns site were much larger than those from the Newberry site. We determined the relationship between the size of individual female wasps and the size of their prey at both locations. Previous studies had concluded that cicada killer hunting is opportunistic, with females provisioning their nests with cicadas of different sex, species, and size in proportion to their relative abundance in the environment. However, we found that individual female cicada killers at these locations exhibited prey specificity by size. Small wasps brought only small cicadas to their nests, as they are likely constrained from carrying large cicadas in flight. Large wasps, not similarly constrained, rarely provisioned with small cicadas. The wasps appear to selectively hunt the largest prey they can carry in flight. Evidence suggests that the cicadas retrieved from wasps at the Newberry site were smaller because small female wasps predominate there, and not because there is a difference in the body size distributions of the cicadas between the 2 local environments.