The adherence of beetle tarsal setae to glass

Summary

Light microscope and SEM micrographs of tarsal adhesive setae from eight species of beetle adhering to glass, and light microscope micrographs of sections from Chrysolina polita (Linnaeus) (Crhsomelidae; Coleoptera) tarsi are presented. Different strategies in achieving ‘efficient adhesion’ and different functional requirements are proposed as the main causes of the diversity of setal structure and distribution observed. The observations of tarsal adhesive setae adhering to glass, and sectioned tarsi suggest that although secretions may be produced and used in adhesion they are not necessarily the most important means of producing the adhesive force. Molecular adhesion is suggested as the most probable and important means of attachment. The role of small projections on the non-adhesive surface of the setal tips as ‘antimatting’ or ‘spacing’ devices is supported by the observations.