Small larvae, 4.5 mm long.
Antenna 5 segmented, basal segment relatively long, 3rd segment unclearly delimited from longer 4th. Ring organ in distal 1/3. Blade arising from apex of 2nd segment, extending to near apex of flagellum; accessory blade seemingly absent. Lauterborn organs absent.
Labrum weakly sclerotised with all S setae simple and fine. Labral lamellae and chaetae absent. Pecten epipharyngis of 3 narrow pointed spines; chaetulae laterales similarly formed. Chaetulae basales present. Ungula U-shaped. Premandible with 3 distinct apical and 1 inner and 1 outer tooth; brush absent.
Mandible with apical tooth about 2x length of combined width of 4 inner teeth. Seta subdentalis slender and long. Seta interna short, with 4-5 plumose branches.
Mentum distinctive, with ventromentum extending over dorsomentum; 3 small ventromental teeth, 13-16 pairs of ventromental teeth. Beard absent.
Anterior and posterior parapods divided, bearing apically mostly fine, simple claws. Procercus higher than wide, with 7 rather short apical anal setae. Body with simple setae.
Acamptocladius larvae have been found in in a German peat pool (A. reissi) and in colonies of Aphanocapsa colonies (A. dentolatens) in Canada. Adults of the third described species, A. submontanus have been found at high latitudes and elevations in Scotland and Sweden (Cranston and Sæther, 1982c).