Medium-sized larvae up to 7 mm long.
Antenna with 7 segments; segment 3 much smaller than fourth; segment 7 hair-like, vestigial. Ring organ just below middle of basal segment. Blade about as long as or slightly shorter than flagellum. Lauterborn organs apparently absent.
Labrum with SI apically split, but without lateral branches. Labral lamella simple, undivided, weakly sclerotized. Pecten epipharyngis consisting of 3 simple, sclerotized spines. Chaetulae laterales simple. Premandible with 1 apical tooth and 1 low, inner, accessory tooth; brush absent.
with apical tooth shorter than combined width of 3 inner teeth. Seta subdentalis relatively long, simple or forked at apex. Seta interna with 1-4 smooth and 3-5 finely serrated branches.
Mentum with 2 median and 4 (5 in abnormal specimens) pairs of lateral teeth; fourth as high as third. Ventromental plate moderately developed with up to 2 vestigial and indistinct setae in beard beneath.
Body with procercus sclerotized with 6-7 anal setae and caudally directed preapical tooth. Anal tubules about half as long as posterior parapods.
The larvae of Paratrissocladius live in sand and mud in streams and rivers, where they build long tubes of sand and detritus.
The genus is Holarctic, Afrotropical and Oriental. The one European species, P. excerptus, is widespread, but especially central and northern. Paratrissocladius furododecimus and P. tokarameneus are known from Japan. Sæther and Wang (2000) treat Afrotropical P. natalensis as a subspecies of P. excerptus (although without knowing the immature stages of the southern African taxon). The genus is represented in the Oriental region (with subspecies, P. excerptus pubis) from Myanmar (Burma) (Sæther and Wang, 2000) and northern Thailand (Cranston pers. obs.). In North America, P. lawrencensis is known from northern parts of the continent.