Larva large (6.7-13.8 mm), with small head (about 0.35 mm long).
Frontoclypeal apotome apparently about as in Polypedilum.
Antenna scarcely longer than length of mandible, 5 segmented, segments 3 and 4 subequal in length, basal segment with seta, blade about as long as segments 2-3, subapical style of second segment distinct, Lauterborn organs weak.
All S setae of labrum simple, labral lamella without apical teeth, chaetae and spinulae absent. Pecten epipharyngis consisting of 3 separate, simple teeth; chaetulae very small. Premandible simple, without brush.
Mandible without dorsal tooth; with 3 inner teeth; without seta interna; seta subdentalis simple, straight.
Mentum with all teeth dark; with 4 smaller equal-sized median teeth and 6 pairs of lateral teeth. Ventromental plates about 1.1 x as wide as mentum, striae continuous.
Anterior parapods strongly reduced, consisting of 2 nearly contiguous welts of minute claws with several teeth. Posterior parapods short, but bulbous, with about 16 small claws. Anal setae short, apically hooked, one wider than high of procercus. Anal tubules large and bulbous.
Collartomyia is known from adults from Zaire (Belgian Congo: Stanleyville) and South Africa. Specimens collected by Arthur Harrison in South Africa: Transvaal, Vereeniging, Vaal River in 1956 and 1958 provide the basis for description of the immature stages (Amakye and Sæther, 1992) and for the observation that larvae feed on pupae of hydropsychid caddis flies.