The wing veins of Zygoptera are provided with spines which differ morphologically according to whether the vein is convex or concave, and in relation to sex (typically in Euphaeidae, Calopterygidae and Chlorocyphidae) and taxonomic position (distinguishing the more primitive Calopterygoidea from Lestoidea and Coenagrioidea. A certain number of variations are constantly associated with the nodal and cubito-anal spaces of the wings, while size appears to be partially related to the surface area, wing chord and aspect ratio.