Pollen grains adhere to the moist mouthparts in the flower visiting beetle Cetonia aurata (Scarabaeidae, Coleoptera)

Abstract

Flower visiting beetles possess numerous structural adaptations of their mouthparts to adhere and ingest pollen grains. Using a Cryo-SEM approach the examination of the mouthparts in rapidly frozen Cetonia aurata (Scarabaeidae) indicates a previously unknown technique of pollen uptake in Coleoptera. Cryo-SEM micrographs of the mouthparts reveal a fluid covering the bristles on the buccal surface. In this way the bristles of the galeae form a wet brush which represents the primary organ of pollen uptake. The fluid improves adhesion of pollen to bristles lacking any specialized adhering surface or highly sculptured cuticle as present in other pollen feeding Coleoptera. The well developed mola region of the otherwise non-biting mandibles of C. aurata indicates that these beetles open pollen grains mechanically before ingestion. Examination of gut content demonstrated that crushed and intact pollen occur in all regions. The Cryo-SEM method represents a new approach to study functional morphology including the interaction of microstructures and fluids on cuticular surfaces of insects.