Sexual dimorphism in the attachment ability of the Colorado potato beetle Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) to rough substrates

Many representatives of the beetle family Chrysomelidae exhibit a distinctive sexual dimorphism in the structure of adhesive tarsal setae. The present study demonstrates the influence of surface roughness on the friction force of Leptinotarsa decemlineata males and females. The maximum friction force of individual beetles was measured on epoxy resin surfaces (smooth and with asperities ranging from 0.3 to 12.0 μm) using a centrifugal force tester. On the smooth surface, no considerable differences between males and females were found, whereas on rough surfaces, females attached significantly (up to two times) stronger than males. Clawless beetles generated lower forces than intact ones, but demonstrated similar differences between males and females. The results indicate that the female adhesive system has its main functional trait in a stronger specialisation to rough plant surfaces whereas the adhesive system of males possess a certain trade-off between attachment to rough plant surfaces during locomotion on vegetation and to the smooth surface of the female elytra, while mating.