Medium-sized larvae, up to 5 mm long.
Antenna subequal to 2/3 length of mandible; 5 segmented; terminal 3 segments subequal in length. Blade extending to apex of flagellum. Lauterborn organs very weak. Style not visible.
Labrum weakly sclerotized. S setae apparently all simple (where visible). Pecten epipharyngis consisting of 3 subequal scales with 4 pairs of single chaetulae laterales on each side. Labral margin, ungula and premandibles weakly sclerotized. Premandible with 3 apical teeth and inner tooth in different plane to apical teeth; brush absent.
Apical tooth longer than or subequal to combined width of 4 inner teeth; distal 3 inner teeth pointed; proximal tooth rounded and slightly longer than other teeth. Seta subdentalis long, extending to distal of inner teeth. Seta interna with 4 simple branches.
Mentum with single median tooth with median projecting nipple; 9-11 lateral teeth present, outermost frequently difficult to discern. Ventromental plate well developed, almost reaching outermost mental tooth on flattened mentum; beard absent.
Maxilla palp rounded with low sensillae and setae. No lamellae present on galea or palpiger base. 1 seta maxillaris present, subtriangular in shape; the remainder simple and narrow, forming a 'crest' on the outer margin of the rounded galea. Appendix seta absent.
Body with separate anterior parapods, with fine claws at apex and shorter claws from base to apex. Posterior parapods well developed, narrow and bearing separate claws. Procercus as high as wide; 7 relatively short anal setae present. Anal tubules clearly shorter than posterior parapods. Body setae absent.
Larval Lapposmittia parvibarba (Edwards), the only species of the genus, were found in springtime in summer-dry pools in birch woods. The species is known from Swedish Lappland and n.e. Russia.