Traction force measurements on male Strepsiptera (Insecta) revealed higher forces on smooth than on hairy substrates

Abstract

The aim of this study was to find out how strongly males of Stylops, having tarsi equipped with tenent hairs and lacking claws, attach to different substrates. We investigated adhesion of S. ovinae to the hymenopteran host abdomen (Andrena vaga), a strongly hairy abdomen of a Bombus sp. and two artificial smooth reference surfaces having different degree of hydrophilicity. In our experiments, the males of S. ovinae developed significantly higher forces on smooth surfaces. However, the forces were significantly lower on all the hymenopteran surfaces used in the experiment. The absence of anisotropy in the force grip in cranial/caudal direction relative to the host might indirectly indicate that S. ovinae generate forces rather by adhesion and not by mechanical interlocking with the host hairs. The tolerance of the attachment system of S. ovinae to the substrate chemistry might be explained by the primary contribution of van der Waals interactions and not capillary forces to adhesion in S. ovinae.