Alarm recruitment, attack behavior, and the role of the alarm pheromone in Polybia occidentalis (Hymenoptera: Vespidae)

Summary

• 1. Defensive behavior in the social wasp Polybia occidentalis involves two steps: first, in response to jarring of the nest, large numbers of adults are recruited rapidly to the outer surface of the envelope. Second, a fraction of these wasps may fly out to attack the intruder.

• 2. Observations suggest that the first step, alarm recruitment, is released by a signal given inside the nest. Experimental introduction into the nest of the odors of various glands and body parts show that venom and venom-bearing structures (venom sac, sting apparatus) elicit alarm recruitment that is indistinguishable from that caused by jarring the nest. The wing buzzing that accompanies alarm recruitment is experimentally shown not to communicate alarm.

• 3. Outside the nest, the odor of venom greatly reduces the threshold for release of attack behavior, but is not itself a releaser of attack. The release of attack behavior requires an appropriate visual stimulus. Dark color of models elicited more attacks than did movement.