Moderate to large-sized larvae, to 15 mm long.
Antenna 5 segmented, basal segment equal to or longer than flagellum. Large ring organ on basal 1/2 of basal segment. Blade arises in distal 1/2 of segment 2, reaching apex of antennal segment, accessory blade short. Lauterborn organs lacking. Antennal seta absent. Style present on segment 2.
SI seta short, blade-like; SII a longer robust blade, SIII seta-like; SIVa 3-segmented. Labral lamellae absent. Pecten epipharyngis a triangular plate divided into 3 lobes with serrate margin. Premandible with 4-6 teeth diminishing in size from apex to base, brush present.
Mandible lacking dorsal tooth, with long apical tooth and 2 triangular inner teeth. Seta subdentalis slender reaching subapical tooth. Seta interna with 2 plumose, 2 simple branches. Pecten mandibularis absent.
Mentum with broad pale median tooth, flanked by 6-7 pairs of dark lateral teeth, first fused to median. Ventromental plates wide (wider than mentum), with fine striae, anterior margin smooth.
Posterior parapod claws simple.
The form of the mentum, with a broad, pale median tooth and 6 or 7 pairs of obliquely arranged, dark lateral teeth, together with 5 segmented antennae and serrated, triangular pecten epipharyngis distinguishes Cryptochironomus larvae from all other Chironomini. Curry (1958a) and Moller Pillot (1978a) dealt with a number of species.
Larvae of Cryptochironomus occur in various substrata in lakes, small streams and larger rivers. Worldwide distribution. About 30 species named from the Holarctic, mostly unknown or inadequately described as larvae.