There is general consensus of monophyly in this superorder, based on reduction of the second valvulae, an ovipositor derived from the gonoplac, and an enlarged precostal region on the forewing.
After the thickened cuticle of the post-oesophageal lumen wall, the cuticle folds to form the outlet valves, 'valvulae', with attached, controlling oblique muscles.
