Medium sized to large larvae, up to 9 mm long.
Antenna with 5 segments; segment 4 longer than, subequal to or shorter than segment 3. Blade at most as long as flagellum, usually distinctly shorter. Lauterborn organs large, longer than antennal segment 3.
Labrum with SI plumose; SII simple or plumose; SIII and SIV normal. Weakly sclerotized labral lamellae present between SI. Chaetae serrate or simple. Pecten epipharyngis consisting of 3 simple, very short spines. Chaetulae laterales simple or serrate; 6 pairs. Premandible with 2-6 teeth; brush absent.
Apical tooth shorter than combined width of 3 inner teeth.
Mentum with 2 median teeth and 5 pairs of lateral teeth. Ventromental plate distinct, extending beyond outer tooth of flattened mentum, often with indication of second plate inside main plate, but this plate is never fully developed; beard absent.
Maxilla with pecten galearis absent. Lacinial chaetae broad at base. Anterior lacinial chaeta slightly to much shorter, triangular; often with apical serrations.
Body with procercus longer than wide, relatively small; with 5-7 anal setae. Anal tubules shorter to longer than posterior parapods. No distinct body setae present.
Larval Parametriocnemus are found in running waters, from pristine to quite nutrient enriched, in all biogeographic regions, In the Neotropics, the genus may be represented only by the Nearctic P. lundbecki, reported from Guatemala and St. Vincent in the Caribbean.