Females of the independent-founding polistine social wasp genera Polistes, Mischocyttarus, Belonogaster and Ropalidia perform conspicuous vibratory behaviors closely associated with the feeding of larvae. Previous research strongly indicates that these are directed toward larvae, although their function(s) remain unclear. Prior hypotheses on function(s) have posited releaser effects on larvae, either stimulating or inhibiting release of larval saliva. P.fuscatus queens perform antennal drumming (AD), a behavior in which they rapidly beat their antennae synchronously on the rims of the nest cells during larval feeding. We used tritiated water as a radiotracer to show that adults regurgitate liquid (extracted from prey) to larvae during AD, but that no larval saliva is released. The observations that AD did not always accompany the feeding of liquid and workers rarely performed AD, even though they fed larvae, refutes the salivary-inhibition hypothesis. AD was first performed on nests when the oldest larvae reached the third instar, the earliest stage that produces measurable volumes of larval saliva. Removal of third-, fourth- and/or fifth-instar larvae from single foundress, pre-pupa-stage colonies did not diminish queen AD rates compared to controls, suggesting that the presence of third- or higher-instar larvae does not have a releaser effect in triggering AD. We propose instead that component(s) in the larval saliva of third instars act as a primer to trigger the onset of AD in Polistes queens.