As many as 162 segments in eight groups are practically used.
The ninth and tenth segments are at most times retracted within the eighth.
With very few exceptions, the larva in this group is active and campodeiform, with cerci and elongate legs as in the Adephaga, but the leg has only four segments and one claw.
Paired processes on the eighth and ninth abdominal segments may be specialized as external organs of reproduction, but these are probably not appendages.
The maxillary palps have usually three, the labial either two or four segments.
