Antenna with 5 segments; segments consecutively smaller. Ring organ on basal 1/3 of segment 1. Blade extending about level of segment 3. Lauterborn organs large, as long as segment 3. Style slightly longer than segment 3.
Labrum with SI bifid; remaining S setae simple. Labral lamellae absent. Chaetae simple to serrate; spinulae simple. Pecten epipharyngis consisting of 3 scales; lateral pair longer than middle scale. Chaetulae laterales simple; chaetulae basales with branched tips. Ungula V-shaped with small quadrate basal sclerite. Premandible simple or weakly bifid; brush absent.
Apical tooth shorter than combined width of 3 inner teeth, scarcely longer than first inner tooth and usually narrower. Outer margin smooth or with faint indication of crenulations near base. Seta subdentalis pointed. Seta interna with 7 simple to weakly serrate branches.
Mentum with median and 6 pairs of lateral teeth; first lateral tooth broader in middle than at base. Ventromental plate triangular; beard absent.
Maxilla with anterior lacinial chaeta relatively broad and flat.
Body with anterior and posterior parapods separate, each with an apical crown of claws. Procercus usually shorter than wide with 6-7 anal setae. Body setae simple.
Everywhere there are difficulties in separating the larvae from some of those of Cricotopus especially where the l4 seta is plumose.
Larval Paratrichocladius are found in all kinds of waters, but especially in cool running waters. Larvae of one species tolerate some salinity, another European species tolerates organic loadings. The genus is found worldwide, except for Antarctica.