Functional morphology of cleaning devices in the damselfly (Odonata, Coenagrionidae).

Among the different micro- and nanostructures located on cuticular surfaces, grooming devices represent fundamental tools for insect survival. The present study describes the grooming microstructures of the damselfly (Odonata, Coenagrionidae) at the adult stage. These structures, situated on the foreleg tibiae, were observed using scanning electron microscopy, and the presence and distribution of resilin, an elastomeric protein that enhances cuticle flexibility, were analyzed using confocal laser scanning microscopy. Eye and antennal grooming behavior were analyzed to evaluate the particle removal efficiency in intact insects and in insects with ablated grooming devices. The grooming devices are constituted of long setae from which a concave cuticular lamina develops towards the medial side of the leg. Each seta shows a material gradient of resilin from its basal to the distal portion and from the seta to the cuticular lamina. The removal of the grooming devices induces a strong increase in the contaminated areas on the eyes after grooming. Further studies on insect grooming can provide valuable data on the functional morphology of insect micro- and nanostructures and can represent a starting point to develop advanced biomimetic cleaning tools.