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 19 Thysanoptera The presence of an eversible, balloon­shaped pretarsal adhesive structure at the distal end of a one­ or twosegmented tarsus is unique to thysanopterans (‘Blasenfusse’) ( Fig. 3e ). Homology of this structure with the arolium is likely as demonstrated by Heming (1970 , 1972 , 1973 ).