Abstract
Similar to other leaf beetles, rosemary beetles Chrysolina americana exhibit a distinct sexual dimorphism in tarsal attachment setae. Setal discoid terminals occur only in males, and they have been previously associated with a long-term attachment to the female's back (elytra) during copulation and mate guarding. For the first time, we studied living males and females holding to female's elytra. Pull-off force measurements with a custom-made tribometer featuring a self-aligning sample holder confirmed stronger attachment to female elytra compared with glass in both males and females; corresponding to 45 and 30 times the body weight, respectively. In line with previous studies, males generated significantly higher forces than females on convex elytra and flat glass, 1.2 times and 6.8 times, respectively. Convex substrates like elytra seem to improve the attachment ability of rosemary beetles, because they can hold more strongly due to favourable shear angles of legs, tarsi and adhesive setae. A self-aligning sample holder is found to be suitable for running force measurement tests with living biological samples.
Highlights
Sexual selection is one of the agents that drive evolution, influencing biodiversity and survival of species [1]
Chrysolina americana is a representative of the leaf beetle family Chrysomelidae (Coleoptera), to which belong several species used so far in detailed attachment studies (e.g. [3,4,6,11,12,13,14,16,17])
The feet of the rosemary beetles were composed of five segments
Summary
Sexual selection is one of the agents that drive evolution, influencing biodiversity and survival of species [1]. Female choice often favours conspicuous secondary sex traits in males [2]. Coloration, visual, acoustic and chemical signals are well-known features facilitating sexual selection in the animal kingdom [1]. In leaf beetles (Coleoptera, Chrysomelidae), numerous species exhibit a distinct sexual.
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