Chemical and Mechanical Signals Trigger Courtship in the Wild Large-Headed Resin Bee Heriades truncorum

Abstract

Hymenopteran females are mostly highly selective, choosing their mating partner according to male quality signals, and may also signal their fertility through chemical advertisement. Male insects, in turn, often display a complex set of courtship behaviors to allure females to mate. In this study we explored the mechanisms triggering courtship behaviors in the oligolectic bee Heriades truncorum. In this species, males perform wing fanning followed by a sideways rocking motion before copulation. We tested the role of chemical cues in partner recognition by exposing males to dead females washed from cuticular extracts (i.e., sex pheromones) that were posteriorly coated, or not, with an extract of unmated females. Additionally, we experimentally reduced male wing length to test whether wing fanning was responsible for triggering sideways rocking motions. We found males to interact more often with females coated by extracts from unmated females, and to display wing fanning in the presence of these pheromones. Male wing fanning was important to perform sideways rocking motions, which are an essential behavior for successful mating and possibly an element used by females to evaluate male quality. Our study shows that both chemical and mechanical signals from female and male bees, respectively, are important elements in the mating system of H. truncorum.