Pupa:  Length of exuviae about 7.4-10.2 mm (fem. 8.17, 7.40-9.30; mle. 9.36, 8.13-10.20) mm; inner margin of wing case about 1.57-2.10 mm long, larger in females.  Exuvia pale Johannsen 1905, fine shagreen over most of the abdominal tergites, stronger at distal ends, but only a posterior patch on segment VI.
The pupa has small frontal warts anterior to the cephalic tubercles, normally base wider than height (35.3 (23-68 µm high and 30-775 µm wide at base) although (Wülker 2009) illustrate a female with an unusually high pair.  The cephalic tubercles differ between males and females.  Those of males are generally larger (about 150-196 µm long and about 1.4-2.4x longer than wide in males; about 65-185 µm long and 1.0-1.4 times longer than wide in females); a seta up to 105 µm long arises just before the tip.  In males only there is a secondary tubercle, with a small seta, attached at the side; secondary tubercle about 81.7 (48-106) µm high and 62 (30-83) µm wide at base.
The respiratory base is slightly kidney shaped, with the basal trunk either kidney shaped or partially constricted in the middle.  Length about 148-165 µm and HR 2.4 (2.2-3.0).  There is a rough patch just anterior to the respiratory base about 37-90 x 24-80 µm which either includes 2 small setae or they are nearby on the lateral side.
About 81 (71-100) recurved hooks at posterior margin of abdominal segment II, central hooks with 2 small knobs on the top and not as downturned as those at either end; hook row continuous, about 57-84% of width of segment (higher values probably due to folding of the abdominal segments of the exuviae).
Pedes spurii B well developed on segment II, usually not seen on segment III; and a large pedes spurii A on segment IV, 191.5 (162-220) µm long, 106.5 (94-119) µm wide; and about 0.21-0.26 of length of segment); other pedes spurii A smaller (about 55-95 µm on seg. V; 56-63 µm on seg VI, with patches of spines).  L-setae present on the posterior margin of the preceding segment of the intersegments III/IV and IV/V, maybe up to 70-90 µm long.
Usually 4.6 (range 1-6) closely appressed spines only at the tip of the caudolateral spur of segment VIII (below).  Fringe of anal lobe with about 105 (80-138) taenie, in a double row posteriorly but may become triple at end, on each side.

Larva and Cytology

Type locality: Johannsen (1905) does not give a type locality but, while noting it is widespread, initially states that it is common in ponds and ditches and, later, in the vicinity of sewage contaminated streams, around Ithaca, New York (1905, 1937).  Townes (1945) lists all localities found in the Johannsen collection as type localities (Noted there as "Johannsen1905" although this is not to imply that they are all this species).
Found: Ontario – Copanspin Farm, Dunrobin (45.75°N, -75.87°W), and South March nr. Mud Lake (44.88°N, -78.27°W), both Carleton Co.;
          Don River, Toronto (Rothfels & Fairlie 1957).
          Arkansas – White River National Wildlife Refuge, Arkansas (Chordas et al. 2004.)
          Illinois – (Johannsen 1905).
          Iowa – (Johannsen 1905).
          Kansas – (Johannsen 1905).
          Michigan – Menominee River, Stephenson (45.42°N, -87.61°W), Menominee Co.
          Nebraska – (Johannsen 1905)
          New Mexico – Eagle Nest Lake (36.55°N, -105.25°W), Canadian River (abt 36.63°N, -104.55°W), Taylor Springs, both Colfax Co.;
          Rio Grande River, (31.75°N, -106,48°W), Dona Ana Co.; Hill Tank (abt. 32.62°N, -104.32°W), Eddy Co.; Pecos River, Puerto de Luna,
          Guardalupe Co., also in San Miguel Co.; Gila River, nr. Virden, Hidalgo Co.; Rio Hondo, 2 ml e. Hondo (33.38°N, -105.26°W),
          Lincoln Co.
          New York – Ithaca, (Johannsen 1905, 1937), also Cornell University, Ithaca (42.45°N, -78.47°W), Tompkins Co.
          Ohio – (Johannsen 1905).
          South Dakota – L. Poinsett, 12 ml n. Arlington; James River, Yankton (42.93°N, -97.33°W), Yankton Co.
          Washington – (Johannsen 1905)
          Wisconsin – Murphys Creek; and Arboretum, (43.03°N, -89.42°W), and University Houses (43.07°N, -89.42°W), Madison, Dane Co.

Note that the data for adult females and the pupae all comes from a single reared egg mass, there is considerable variation in some characters - mostly these characters are related to overall size of the individual.  Chironomus sp. B of Jacobsen (2008) is probably this species.

Some information on arm F is given in Fig. 3 of Martin (1979) and Wülker, Devai & Devai (1989).  The karyotype was described in some detail in a Report to New Mexico Energy Institute by Martin, Sublette and Sublette (1979).  Also the chromosomes and chromosome polymorphism was described by Rothfels and Fairlie (1957) (see link below).