Ultrastructure of attachment specializations of hexapods (Arthropoda): evolutionary patterns inferred from a revised ordinal phylogeny Author R. G. Beutel Author S. N. Gorb text J. Zool. Syst. Evol. Research 2001 39 177 207 journal article 10.1046/j.1439-0469.2001.00155.x 95b3d62f-8fcc-4088-873f-b33f4a63d3fc 2360323 10 Blattodea Tarsi are five­segmented. An arolium is present or absent. Tarsomeres 1–4 are usually equipped with euplantulae ( Figs 3a,h , 4C ). Reduction of adhesive structures occurs often in cavernicolous forms ( Roth 1991 ). The arolium cuticle bears chitinous threads oriented at some angle to the surface ( Roth and Willis 1952 ).