Potential role of environmentally derived cuticular compounds in stingless bees

Body surfaces of organisms must prevent desiccation and inhibit the intrusion of harmful compounds and organisms. In insects, these functions are fulfilled by their cuticle, of which the external one represents a lipid layer that comprises different compound groups with various functions. In the highly social stingless bees, cuticular compounds are either produced by the bees themselves (i.e., genetically determined) or acquired from plant resins (i.e., environmentally derived). While genetically determined compounds protect their bearers against desiccation and convey information among and between species and colonies, environmentally derived compounds substantially increase the surface’s chemical diversity, but their functional role remains unclear. We investigated whether resin-derived compounds may affect predators by testing whether ants showed a different behavior when offered a choice between one bee species with and one without resin-derived cuticular compounds and when faced with cuticular extracts of these two species. We additionally compared weight loss through desiccation of living bees and the rate of developing mold of dead bees between the two bee species. We found that ants preferred bees without resin-derived compounds and were more repelled by extracts of bees with resin-derived compounds. The rate of developing mold did not differ between the two bee species and weight loss through desiccation primarily depended on the bees’ body sizes, but not the species and thus cuticular chemistry. We therefore suggest that environmentally derived compounds may provide an advantage to their bearers as they can protect them against predators.