Minute to moderately-sized larvae, fourth instar 2-6 mm long. Head capsule elongate and nearly parallel-sided, or less elongate and tapering.
Antenna 5-segmented, 1/3 to as long as head capsule length; basal segment slightly longer than flagellum to shorter than the very long flagellum, ring organ and basal setal mark close to base, second setal mark mostly at about 2/3; second antennal segment 2 or 4-5 times as long as combined length of 3-5, extreme base only or basal half unsclerotized; segments 3 and 4 short; segment 5 long, thin, thread-like. Lauterborn organs weak, style distinct. Base of blade sclerotized, blade extends beyond flagellum when most of 2nd segment sclerotized, long, but shorter than second segment when basal half of 2nd segment unsclerotized. AR 0.4-0.8 when most of second antennal segment unsclerotized, 0.9-1.0 when mostly sclerotized.
SI simple or with a few apical teeth, other S setae simple, no labral lamellae, at least 3 chaetae and 3 spinulae. Pecten epipharyngis of 3 simple scales. Chaetulae laterales 4-6 pairs, median pair strong, other apically plumose with long points; chaetulae basales apparently apically simple. Premandible simple and broad, but sometimes with inner hump which may appear as second tooth; without brush.
Mandible with 3 (1 species) or 4 inner teeth, apical tooth shorter than combined width of first 2 inner teeth, seta interna with about 6 strongly branched branches; seta subdentalis strong.
Mentum with either 2 median teeth and 3 pairs of lateral teeth with second tooth lower than first and third and with 2 additional teeth placed ventrally of lateral teeth, or with single triangular to rounded median tooth teeth and 5 pairs of lateral teeth with third tooth lower than neighbouring teeth. Ventromental plates essentially absent. Setae submenti simple, situated either just posterior to base of outer lateral mental tooth or at same level, but more median.
Body elongate, abdominal segments longer than wide. Anterior parapods short, separate, smooth or indistinctly to distinctly serrate claws. Posterior abdominal segment with several distinct setae. Procercus short, as high as wide; with two long, strong anal setae; lateral procercal setae long, placed at base of procercus on abdominal segment and not on procercus. One species with procerci placed at apex of long projection. Supraanal seta well developed. Posterior parapods narrow, digitiform, mostly parallel-sided, ventrally oriented, with 12-16 smooth apical claws. Anal tubules shorter than posterior parapods, bluntly triangular to digitiform, more or less constricted at extreme base.