Chemical Signatures of Reproduction and Nestmate Identity in the Socially Flexible Sweat Bee, Lasioglossum baleicum

Abstract

As a member of the family Halictidae, an extremely socially diverse group of insects, L. baleicum is one of the only members of the fulvicorne species group known to exhibit solitary and non-delayed eusocial polymorphism (Cronin and Hirata, 2003). This polymorphic species also displays a nontrivial frequency of workers with highly developed ovaries. Coupled with observations of drifting behavior, in which female workers leave natal nests to found new nests or join others to care for unrelated broods, conflicts between queens’ and workers’ evolutionary interests arise. It is in the queen’s best interest for workers to remain and care for her brood, increasing her reproductive success. However, a worker may achieve more reproductive success by laying her own brood rather than caring for a queen’s brood. This suggests that there must be some mechanism by which the queen maintains her status as the dominant reproductive. Olfactory cues have been previously shown to be integral to dominance hierarchy maintenance in closely related species. This study addresses how L. baleicum uses chemical signaling to relay important information regarding social caste occupation and reproductive status by chemically profiling the pheromonal ratios of social castes and identifying compounds used to establish dominance in nests by queens.