Medium sized larvae, up to 6.5 mm long. Frequently with brown thoracic striations. Head capsule mostly yellowish with dark postoccipital margins.
Antenna with 5 segments; segments consecutively smaller until fifth, which is subequal to slightly longer than fourth. Ring organ low on basal segment. Blade shorter than flagellum. Lauterborn organs distinct, but shorter than segment 3.
Labrum with SI bifid or occasionally with 6-8 apical teeth. Pecten epipharyngis consisting of 3 smooth scales, subequal or with outer scales broader. 3-4 chaetulae laterales present, simple; chaetulae basales also simple. Premandible with 1 apical tooth; brush absent.
Mandible with apical tooth shorter than combined width of 3 inner teeth. Seta subdentalis with apical hook. Seta interna with 5-6 branches; simple or with bluntly plumose apices.
Mentum with two median teeth with or without accessory teeth; 5 pairs of lateral teeth present. Ventromental plate broad, extending beyond margin of outer mental tooth; with numerous setae in beard beneath.
Maxilla with pecten galearis well developed. Anterior lacinial chaeta often triangular.
Body with parapods normally developed; claws of anterior parapods with some inner teeth. Anal tubules short. Body setae short or absent in the fuscipes group, relatively long in the atripes group. Procercus higher than wide, usually with distinct medioposterior spur; with 3-5 anal setae.
Larval Rheocricotopus are rheophilic on submerged macrophytes, cobbles etc. in streams and rivers, with rare records from the splash-zone of the littoral of lakes.
The genus is worldwide, perhaps with the exception of the Neotropical region.