On account of the great extension of the metathorax and the haunches of the large hindlegs, the first abdominal sternite is wanting, and the second is - the stylets.
Smaller appendages (such as the stylets of male cockroaches) may be carried on the ninth segment.
The appendages of the abdomen are called cerci, stylets and gonapophyses.
The stylets, when present, are placed on the ninth segment, and in some Thysanura exist also on the eighth segment; their development takes place later in life than that of the cerci.
Metanemertini, in which the nervous system lies inside the dermal muscles in the parenchyma; the mouth lies in front of the level of the brain; the proboscis as a ru'e bears stylets; the intestine nearly always has a caecum.