Changes in the temporal pattern of antennal drumming behavior across the Polistes fuscatus colony cycle (Hymenoptera, Vespidae)

Abstract

Social wasps in several genera exhibit a diverse array of conspicuous vibrational behavior patterns closely associated with larval feeding. Polistes, as the only genus in which these substrate-borne mechanical signals have been studied in some detail, is a useful system for understanding their functions. Most Polistes species examined perform antennal drumming (AD) in the context of feeding prey liquid to larvae. Two existing hypotheses on the function of AD propose that it is a behavioral releaser signal that regulates the release of larval saliva, but with opposite effects. One proposes that AD stimulates larvae to release their saliva for the drumming adult to imbibe, whereas the other proposes that AD inhibits saliva release. A recently proposed third hypothesis argues instead that AD has a modulatory effect on development: exposure to high levels of AD biases larvae toward a worker phenotype as adults. While the larval-saliva-release hypothesis for AD function has little support, predictions made by both the inhibition hypothesis and the mechanical switch hypothesis are yet to be tested within the broader ontogenetic framework of the Polistes colony cycle. We investigated the contexts, rates of performance, and actors associated with AD across 13 weeks of the P. fuscatus colony cycle. Mean colony-wide rates of AD were high during pre-emergence and early post-emergence stages, but dropped dramatically following the third week after the first workers emerged. This variation in the temporal pattern of AD was correlated neither with the rate at which larvae were fed liquid, the number of larvae on the nest, nor with the adult-to-larva ratio, but was solely a function of colony stage. In contrast, rates of feeding liquid to larvae varied only as a function of the number of larvae in the nest. Queens drummed and fed liquid to larvae at much higher rates than did workers. Queen AD and feed-liquid rates decreased after the third week of worker emergence. During the same period, total feed-liquid rates of workers became as high as levels of queens during pre-emergence. Colony-wide AD rates dropped dramatically because workers seldom drummed while feeding liquid to larvae. The mean duration of AD bursts for queens also decreased after the second week of worker emergence. These results fail to support the salivary inhibition hypothesis, but provide indirect support for the mechanical switch hypothesis on AD function.