Small to medium-sized larvae, up to 5 mm long.
Antenna with 5 or 6 segments, when 5 segmented, segment 2 much longer than 3rd. Small single Lauterborn organ and stronger style both on apex of 3rd segment. Ring organ in proximal 1/4 of segment 1, seta absent. Blade apical on 2nd segment, subequal to flagellum, accessory blade absent.
SI and SII fine, seta-like, SII a long broad blade, flanked by 1or 2 long, blade-like chaetae; SIII very small, seta-like; SIVa long, 3-segmented. Labral lamellae absent or weak. Pecten epipharyngis a small triangular plate, cleft medially. Median pair of chaetae laterales broad, serrate along inner margin, remainder more slender. Premandible with 3 teeth, brush absent.
Mandible lacking dorsal tooth, with apical tooth and 2 or 3 triangular, inner teeth. Seta subdentalis long, blade-like, or shorter. Seta interna of 4 serrate branches. Pecten mandibularis of 3-5 long lamellae.
Mentum with narrow to broad median tooth, paler than or concolourous with 6-7 pairs of lateral teeth on each side. Ventromental plates as wide as mentum, widely separated medially, with distinct striations. Setae submenti simple.
Palp moderately well developed, 1st segment about 1.5-2 times as long as wide; whole palp subequal in length to antennal segment 1.
Posterior parapod with simple claws. Lateral and ventral tubules absent.
Larvae apparently may be distinguished from those of Paracladopelma by their 6 segmented antennae. Together these 2 genera differ from all other Chironomini in the combination of seta-like SI, and strong, blade-like SII flanked by 1 or 2 pairs of blade like chaetae. Reared material from Australia suggests the generic distinction from Paracladopelma may not be valid.
Larvae of Saetheria inhabit sandy substrata of lakes and streams in the Holarctic and perhaps Australia.