Larval stages are poorly known, but those described are slender, narrowed anteriorly, with groups of ventral spicules on creeping welts. The larva is amphipneustic (having only the anterior and posterior pairs of spiracles). The mandibles are simple, hooked, and without additional teeth. The parastomal bars are long, thin structures, fused to the tentoropharyngeal sclerite. The hypopharyngeal sclerites are long separate or connected by a sclerotized bridge; the anterior spiracle (prothoracic spiracle) is a rosette or branched. The posterior spiracles (on the anal segment) are usually on two cylindrical lobes. Each spiracle has three slit or oval openings and three or five groups of interspiracular hairs that are branched in some species.