Comparison of tarsal and cuticular chemistry in the leaf beetle Gastrophysa viridula (Coleoptera: Chrysomelidae) and an evaluation of solid-phase microextraction and solvent extraction techniques

Tarsal substrate adhesion in insects is based on the effect of a thin film of liquid in the contact zone, which is deposited as droplets on the surface an insect has walked on, but as yet, little is known about the chemical composition of the liquid. In the present study, interference reflection microscopical images of the tarsal contact and footprints of Gastrophysa viridula (Coleoptera: Chrysomelidae) are depicted and the chemical composition of tarsal liquids and cuticular components are investigated by means of solid-phase microextraction and solvent extraction of whole beetles and footprints. Based on this comparative methodical approach, we are first to provide evidence from direct sampling for the chemical congruence of cuticular lipids and tarsal liquid in beetles. Furthermore, differences resulting from the applied sampling techniques are assessed and advantages of the respective methods are discussed.