Morphology of arolia in Auchenorrhyncha (Insecta, Hemiptera)

The pretarsal arolium serves as an attachment device in many groups of insects, enabling them to walk efficiently on smooth surfaces, where claws alone do not provide sufficient foothold. The arolia of representatives of all major lineages of Auchenorrhyncha are described and illustrated, mainly using scanning electron microscopy and histology. Glands inside the lumen of the arolia are described for the first time in this group. It is shown that the morphology of arolia within Auchenorrhyncha differs considerably. Some of them are even distinctly bilobed. The cuticle of the contact zone is thickened and formed of branching chitinous rods. In some cases, two layers of rods oriented in different directions were found. An extended definition of "arolium" is proposed.