Medium-sized larvae, up to 9 mm long.
Antenna 5 segmented, basal segment longer than flagellum, segments 2 and 3 subequal. Long blade fused to base of segment 2, reaching beyond flagellum, accessory blade absent. Lauterborn organs absent. Style on apex of 3rd segment. Antennal seta absent.
SI seta-like; SII very long, blade-like, much longer than SI, SIII very small, seta-like; SIVa long, 3-segmented, SIVb not identified. No chaetae. Labral lamellae absent. Pecten epipharyngis a single distally trifid plate.
Premandible with 2 large apical teeth and 4 smaller teeth proximally, brush absent. Mandible lacking dorsal tooth, with elongate, apical tooth about as long as 1 or combined 2 inner teeth. Seta subdentalis slender. Seta interna 4-branched, distal 2 strong, uniserrate, other 2 slender, simple. Pecten mandibularis absent.
Mentum with broad median area, paler than laterals and sometimes laterally notched, often paler than laterals; flanked by 7 pairs of dark, lateral teeth. Ventromental plates each about 2x as high as wide, 3/4 width of mentum, weakly striate. Setae submenti simple.
Palp well-developed, longer than basal antennal segment.
With claws of posterior parapods simple.
The form of the pecten epipharyngis, a single distally trifid scale, is sufficient to distinguish Harnischia larvae from all other Chironomini.
Larvae of Harnischia occur in soft sediments of lakes and larger rivers. The genus has a worldwide distribution, with possible exception of the Neotropical region. There are perhaps eight known Holarctic species, several of which, according to Sæther (1971a), are tentatively placed as their immature stages are unknown.