Sensu Keyl and Keyl, 1959
Body
Living larvae are red. Four ventral tubules on the 11th abdominal segment of equal length and 1 pair of lateral tubules on segment 10. Procercus and anal tubules present (Wiederholm, 1983; Vallenduuk and Moller Pillot, 2002).
Head
Width 460 - 664 µm, the frontal apotome is light and the gula is darkened (Vallenduuk and Moller Pillot, 2002).
Antenna
The antenna consists of 5 segments. Length of 1st antennal segment/2nd segment > 3.65 (Vallenduuk and Moller Pillot, 2002). The blade is not longer than the flagellum. Lauterborn organs distally on the second segment.
Mentum
The mentum has three median teeth and 6 pairs of lateral teeth. Mentum size (see glossary) is 56 - 75 µm. Mentum type 1 Mentum type 1 pict (rarely 2). Ventromental plates with 42 - 50 striae and 42 - 46 outer hooks (Vallenduuk and Moller Pillot, 2002).
Labrum
SI is plumose and labral lamellae are normal.
Mandible
The mandible with a pale dorsal tooth, apical tooth dark and 3 inner teeth. The inmost tooth paler than the other teeth (type 1 or 2) Chiron mand l Chiron mand ll. The pecten mandibularis is present and seta interna with 4 toothed and plumose branches.
Differential characteristics
Chironomus is the only genus with 2 pairs of tubules on the 11th segment Chir 4 ventral tubules. Some species lack the ventral tubules (C. salinarius Chir no tubules, C, nudiventris and C. agilis). C. salinarius occurs only in brackish and salt water. The latter two species have a pair of lateral setae on segment 10 Chir 2 lateral tubules. These two species can be separated from Einfeldia pagana by the absence of a pit on the frontal apotome.
C. annularius can be separated from all other Chironomus (except C. cingulatus and C. melanotus) by:
Two pairs of ventral tubules on segment 11 and 1 pair of tubules on segment 10.
Gula dark, inmost mandibular tooth less dark than the other teeth (type 1 or 2), mentum type 1 (rarely 2). Ventromental plates with 42 - 46 outer hooks and 42 - 50 striae. Width of the head 460 - 664 µm. Length of 1st antennal segment/2nd segment > 3.65. C. melanotus has a mentum of type 2 or 3 (rarely 1), a head width of 581 - 706 µm and a darker gula. C. cingulatus has 38 - 43 outer hooks, head width of 623 - 664 µm and length of 1st antennal segment/2nd segment < 3.65.