Large to very large-sized larvae, to 60 mm long.
Frontoclypeal apotome present, isolated labral sclerite 2, labral sclerites 3 and 4 fragmentary.
Antenna with 5 segments. Ring organ in proximal 1/2 of 1st antennal segment. Lauterborn organs opposite on apex of 2nd segment. Antennal blade not extending to flagellum apex, accessory blade about 1/2 as long as segment 2. Style on apex of 2nd segment, about as long as segment 3.
SI seta plumose on each side, exceptionally on one side only (s.g. Camptochironomus), SII simple, SIII short, simple, SIVa simple sensillum. Labral lamellae normal. Pecten epipharyngis simple, of 15-30 small teeth. Premandible with 2 apical teeth, exceptionally 5 in some Neotropical and AustroOriental species, brush strong; seta premandibularis simple.
Mandible with pale dorsal tooth, apical tooth dark, with 3 pointed inner teeth. Seta subdentalis simple (a few teeth in 1 Neotropical species), extending to base of apical tooth. Seta interna of 4-5 plumose branches. Pecten mandibularis with toothed lamellae. All species basally with radially-arranged striae or furrows on outer surface.
Mentum with trifid median tooth with outer toothlets variable in size and degree of fusion, but usually smaller than median tooth, 6 pair of laterals, regularly decreasing in size or first pair closely approximated; 4th lateral may be smaller than 5th and 6th. Ventromental plates separated medially, about as wide as mentum, with numerous fine striae.
Sometimes with lateral tubules, nearly always with at least some evidence of 2 pairs of ventral tubules (absent in some saline species). Anal tubules very variable, absent in saline species.
Larvae of Chironomus graze on detritus or are filter-feeders, predominantly in soft sediments of standing water, more rarely in flowing water. A few species are halophilous, or halobiontic. Some species prefer or are restricted to humic water.
With several hundred species of Chironomus, has a worldwide distribution ranging from the tropics to the arctic.