# Sexual Dimorphism of Tarsal Attachment Devices and Their Relation to Mating in Coccinellidae

## TL;DR

This study explores how male and female coccinellid beetles have evolved different attachment structures for mating, with males developing specialized setae and claws based on the texture of female elytra.

## Contribution

The study reveals novel morphological adaptations in male coccinellid attachment devices linked to female elytral surface structures and body size.

## Key findings

- Disco-setae in males are present only in some species and are localized on hairy pads used during mating.
- Morphology of discoid setae correlates with female elytral texture, with larger tips on smooth elytra and smaller on hairy ones.
- Claw dimorphism is more pronounced in males with hairy elytra and absent in larger species with pad dimorphism.

## Abstract

This study investigates the coevolution of male attachment devices and female elytral morphology in coccinellid beetles, focusing on the sexual dimorphism of claws and adhesive pads. We analyzed 11 species from different tribes with different feeding regime, examining the structure of male and female attachment organs (claws and hairy pads) in relation to the surface structure of female elytra. Our findings show that disco‐setae, which enhance adhesion during mating, are present only in males of some species and are localized on the hairy pads of their legs. These setae exhibit morphological adaptations based on the surface structure of female elytra, with larger discoid setal tips in species with smooth elytra and smaller tips in those with hairy elytra. Additionally, male beetles with hairy elytra possess dimorphic claws, which enhance attachment efficiency compared to species with smooth elytra, where claw dimorphism is less pronounced. Our results reveal that sexual dimorphism in hairy pads is more pronounced in larger species, where claw dimorphism is absent, while in smaller species, claw dimorphism alone suffices for effective attachment. These findings contribute to a deeper understanding of the evolutionary dynamics shaping attachment adaptations in Coccinellidae, with implications for reproductive strategies, pest management, and ecological interactions in this diverse beetle family.

We explore the coevolution of male attachment devices and female elytral morphology in coccinellids. Specifically: (1) Disco‐setae are present in males of some species, located on the hairy pad which during mating hold on female elytra. (2) The area of male disco‐setae is extended when females have smooth elytra, and reduced when females have hairy elytra. (3) Males with hairy elytra possess bifid claws. (4) Sexual dimorphism in pad setae evolved only in larger species, where claw dimorphism is absent.