The ninth and tenth segments are at most times retracted within the eighth.
As many as 162 segments in eight groups are practically used.
The segments of each ch~omosome are usually twisted upon.
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.
The head - carrying feelers, mandibles and two pairs of maxillae - is succeeded by the three thoracic segments, each bearing a pair of strong five-segmented legs, whose feet, like those of the adult, carry two claws.