What’s on the Menu: Floral Tissue, Pollen or Nectar? Mouthpart Adaptations of Anthophilous Beetles to Floral Food Sources

Abstract

Anthophilous Coleoptera are frequent flower visitors, and many have specialised mouthparts to feed on floral tissue, pollen grains and/or nectar. Although not all of these flower visitors are pollinators, many beetles pollinate various plant families. The present chapter deals with the mouthpart morphology and feeding preferences of beetles. The evolutionary pathways to flower visiting and pollination by beetles are discussed in the context of mouthpart specialisations. Compared to destructive floral tissue feeding, many pollen-feeding beetles have lost cutting or biting structures on the mandibles and maxillae. Instead, their characteristic mouthparts include characteristic types of hairs, bristles or setae on the maxillae, responsible for collecting and transporting food inside the preoral cavity. Massive, paired mandibles with a lacinia mobilis and a prominent molar crush pollen like mortar and pestle. Adaptations to nectar feeding include either elongated maxillary palps or an elongation of the hairy galea. Although Coleoptera are considered rather unspecialised pollinators, various plant species have evolved floral syndromes, such as flower odour, colour and morphology, to attract anthophilous beetles. As such, specialised beetle pollination systems are found across various plant families.