Medium-sized larvae, up to 8 mm long.
Frontal apotome and clypeus narrowly separate. Supraorbital seta (S7) and genal seta (S10) branched; remaining head capsule setae simple. Labral sclerites SI and SII separate.
Antenna with 4 segments, the segments being consecutively shorter; segment 1 weakly curved. Ring organ on basal 1/3 of segment 1. Blade longer than flagellum. Lauterborn organs and style distinct but much shorter than segment 3.
Labrum with SI plumose; remaining S setae simple. Labral lamellae consisting of 2 broad, pectinate lobes. Chaetae serrate; spinulae simple. Pecten epipharyngis consisting of 3 smooth scales. Chaetulae laterales simple to serrate; chaetulae basales present. Ungula with well developed basal sclerite. Premandible broad, weakly bifid at apex; brush absent.
Apical tooth shorter than combined width of 3 inner teeth. Seta subdentalis long, apically pointed and slightly curved. Seta interna with 7 plumose branches.
Mentum with 1 median and 6 pairs of lateral teeth present; first lateral teeth elongate; fifth and sixth lateral teeth appressed to each other. Ventromental plate small; very short beard present. Setae submenti arising about midway between mentum and postoccipital margin.
Maxilla palpiger with simple to serrate lamellae. Galea with several narrow lamellae and without pecten galearis. Setae maxillaris simple.
Body with separate parapods, each bearing an apical group of claws. Procercus 1.5 to 2 times as long as wide, with 7 anal setae; without spur. Anal tubules shorter than length of posterior parapods.
Larval Euryhapsis are found in clean (perhaps only near pristine) low and middle-order flowing waters in the Palaearctic and western Holarctic region. In California an undescribed species is known from middle elevation streams in the Sierra Nevada mountains.