In insects with poorly defined segmentation behind abdominal segment IX, the complex formed of abdominal segments X and XI, with its cerci, and the telson. In such adult insects, the telson and abdominal segment XI are entirely membranous (with the frequent exception of the cerci).

For ♂: anal cone, anal lobe, anal segment, harpago, harpe, lobe of tenth sternite, tenth abdominal segment, tenth segment, tenth sternites; for ♀: anal cone, anal membrane, anal protuberance, anal segment, peri-anal membrane, segment X, tenth segment; for pupae: anal lobe, anal segment, genital pouch, ninth sternite, tenth abdominal segment, tenth segment, segment X.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith