Age-related changes in cuticular hydrocarbon bouquet and same-sex sexual behavior of mason bee males (Osmia cornuta and O. bicornis)

Finding a mate is the central task in the lives of many male insects. In many solitary bees, sexual competition between males is high due to monandry and a pronounced male-biased sex ratio. Males searching for females will inspect and mount any object of suitable size and habitus. Species, sex, and reproductive status are encoded in the bee's bouquet of cuticular hydrocarbons (CHCs) and can only be identified at a short distance from the object encountered. In two species of mason bees, this CHC-based system for recognizing newly emerged, virgin females is not error-free. Newly emerged individuals of both sexes carry similar CHC bouquets, facilitating the confusion of newly emerged males with newly emerged, virgin females. Misidentification leads to same-sex sexual behavior by males seeking a mate. However, individuals of both sexes modify their CHC bouquet sex-specifically within a few days. The changes in the bouquet prevent further sexual harassment. In addition, within 3 days of emergence, males begin to release species-specific carboxylic acid esters, which may act as courtship-inhibiting pheromones to extend the range of their sex-specific scent tag. Due to the pronounced protandry of both species, SSB is restricted to the early flight season, when females are not yet present, and imposes no apparent cost on the two males involved.

Automated summary

Finding a mate is crucial for many male insects, and in solitary bees, high sexual competition exists due to monandry and male-biased sex ratios. Chemical cues, such as cuticular hydrocarbons, are used to recognize newly emerged, virgin females, but errors can lead to same-sex sexual behavior. However, both males and females modify their chemical bouquet within a few days to prevent further sexual harassment. Additionally, males release species-specific pheromones that may inhibit courtship behavior.