Hunting Social Wasp Interactions: Influence of Prey Size, Arrival Order, and Wasp Species

Abstract

To determine the effects of wasp species, nest affiliation, arrival order, and prey size on choice of and access to prey and on agonistic behavior among hunting wasps, I observed interactions among Polybia occidentalis and Polybia diguetana (Hymenoptera: Vespidae) prey foragers in Guanacaste, Costa Rica. Wasps were trained to forage on Bagisara repanda (Lepidoptera: Noctuidae) larvae at a test site, and trained wasps were used in experiments. The presence of another forager influenced the choice of an access to prey by hunting wasps. In choice tests, both species preferentially hovered near prey occupied by another Polybia forager rather than unoccupied 0.5—cm pieces of prey, but their subsequent responses differed. Polybia occidentalis foragers tended to land with other Polybia foragers of either species and to gain access to the occupied prey. Polybia diguetana foragers did not land preferentially with other Polybia. In intra— and interspecific tests of wasp pairs, tolerance among wasps varied with prey size. The greatest percentage of highly agonistic activity occurred when the resident was on the largest piece of prey that she had a chance of being able to carry away. As the size of prey increased above that, the percentage of highly agonistic behavior decreased. In intraspecific tests, P. occidentalis foragers did not treat nestmates preferentially. In cross—species tests, both prey availability and the arrival order of wasps affected the tolerance of wasps. There was a lower overall percentage of agonistic behavior in tests where the slightly larger wasp, P. occidentalis, arrived first. Hunting Polybia foragers behaved as if using the following rules: (1) If a forager was able to fly off with prey and avoid conflict, she picked up the prey and fled. (2) She fought if she had a chance of excluding others and monopolizing the prey. (3) If the prey was large, the two foragers split it. Both the defensibility of the prey and the ability of the wasps to take advantage of this defensibility structured the interactions among hunting wasps. These interactions influenced the hunting success of wasps and are therefore determinants of nest productivity. Interactions among foragers thus may bear on the diversity and abundance of social wasps.