Species 2j. C. crassicaudatus Malloch, 1915

Description of Malloch (1915):

Male.—Yellowish green, opaque.  Head yellow; scape of antennae and base of flagellum yellowish, the remainder fuscous, plumes pale brown; palpi brownish yellow.
Mesonotum with gray or brown vittae, the disc with faint whitish pruinescence; sternopleura reddish except on upper margin; postnotum brown.  Abdominal segments each with the basal half blackish brown, the dark color usually extending posteriorly on median line, or with a broad brown band on basal half which does not extend to the extreme base.  Legs greenishyellow, knees,and apices of tibiae and of the tarsal joints narrowly brown.  Wings as in stigimaterus (?).Frontal tubercles large; palpus as in Figure i, Plate XXXII.  Hypopygium as in Figure 13,Plate XXXIII; lateral view as in Figure 13, Plate XXXIV.  Surface hairs on fore tarsi and mid and hind legs shorter than in stigimaterus (?) ; basal joint of fore tarsi slightly less than one fourth longer than fore tibiae (98:80). Venation as in stigimaterus (?).
Length, 8 mm.

Adult Adult redescribed by Townes (1945), with some additional data by Sublette and Dendy (1957) and Sublette and Sublette (1971).

Male:  Wing length - 4.87 (3.77-6.0) mm; VR - 1.03 (1.00-1.05) or 0.97 (0.95-1.00).  AR - 4.52 (4.15-4.87); LR - 1.25 (1.11-1.35).
Large and very stout.  Ground color light or pale brown, thoracic markings ochraceous brown.
Head - frontal tubercles moderately large - 57 (35-82) µm; Clypeus of moderate size, clypeal setae - 60 (44-76)
Thoracic setae - dorsocentral - 47 (29-59); prealar - 10 (8-13); scutellar - 48 (36-62).
Legs- pale brown, apices of tibae and of tarsal segments brown.  Fore tarsus with short sparse beard, fore LR - 1.28; mid LR - 0.48; hind LR 0.54.
Leg proportions (units):

	Fe	Ti	Ta1	Ta2	Ta3	Ta4	Ta5	LR	F/T	BR
PI	130+	220	290	130	80	85	40	1.23-1.33	?	-
PII	240	210	110	60	40	30	25	0.42-0.53	1.00-1.14
PIII	290	300	170	90	80	-	-	0.50-0.57	0.97

Male hypopygium (left) and superior volsella (right) of Chironomus crassicaudatus

Abdominal tergites each with a central brown transverse band with indefinite edges, VI and following segments mostly brown.  TIX with perhaps about 9-20 setae, apparently in individual pale spots enclosed in a paler area.
Genitalia large and heavy, with Superior volsella essentially an E-type, closest to E(i) of Strenzke (1959), but with a blunter, more rounded end. Inferior volsella bending inwards towards each other and extending well up to past the mid-point of the gonostyle, which is broad and narrows evenly from about a third of its length.

Female:  Townes notes as "similar to male except for the usual sexual differences".

Molecular data.  There is mtCOI sequence in GenBank (e.g. KR085208), as well as specimens in the BOLD database.
The molecular sequence, along with the modified male hypopygium, indicates that this species is less close to the other three species of the staegeri-group.

Found: Manitoba - Lake Winnipeg (Sæther 2012)
            Ontario - Trenton, Ottawa & Point Pelee (41.959°N, 82.518°W) (Townes 1945)
            Alabama - Auburn (Sublette & Dendy, 1957)
            Arkansas - Marianna, Lee Parish; White River National Wildlife Refuge, Arkansas (Chordas et al. 2004)
            Florida - Cannon Lake, Polk Co., Lake Apopka, Orange Co. (Frouz et al. 2002); Miccosuccee Lake;
            Little Manatee River; Myakka River S.P.; Kissimmee Prairie Preserve S.P. (all BOLD).
            Georgia - 5 miles w. Athens, Lagos Pond, nr Athens & 5 ml w. Athens & Lagos Pond, Athens (33.97°N, -83.50°W), Clarke Co.;
            Lullwater Lake, DeKalb Co.
            Illinois - 3.5 ml n.e. Mahomet, & Homer Park, Champaign Co.; Peoria, Peoria Co. (Type), Homer Park, Champaign Co. (Townes 1945)
            Indiana - Shafer Lake.
            Iowa - Davenport & Kossuth Co. (Townes 1945)
            Kansas - Potters Lake, Lawrence, Douglas Co.; State Park, Leavenworth, Leavenworth Co. (Townes 1945)
            Louisana - Natchitoches, Natchitoches Pa.
            Maryland - Fenwick, Charles Co. (Townes 1945)
            Michigan - Midland Co. (Townes 1945)
            Minnesota - Hennepin Co. & Traverse Co. (Townes 1945)
            Nebraska - no locality (Townes 1945)
            New Jersey - Wildwood (Townes 1945)
            Ohio - Maumee Bay, Toledo (GenBank KP954640).
            Oklahoma - Buncome Creek Bay, Lake Texoma, Marshall Co.; Oklahoma City (Townes 1945)
            Pennsylvania - Philadelphia (Townes 1945)
            South Dakota - Yankton; Lake Francis Case; Gavins Point National Fish Hatchery.
            Tennessee - Oak Ridge, Anderson Co.; Reelfoot Lake.
            Texas - Lake Lomalta and Katherine (Paratypes), Brownsville & Lake Refugio at Twin Mott (Townes 1945)
            Wisconsin - Lake Wingra (43.05°N, -89.42°W), Dane Co., East Horsehead Lake, Oneida Co.

            Lakes and other lentic habitats, where it can be a pest (Frouz et al. 2002).  To depth of 5.5 metres (Sublette and Dendy (1957).

Identification:  The larva of this species can be recognized by the combination of characters:  large plumosus-type; very dark gula but pale frontoclypeus; greater than 80 striae on ventromentum with a crenullated anterior margin.  Possibly it may be differentiated from C. staegeri or C. frommeri by the fine striae in the anterior 1/3 to the margin.
Although placed in the staegeri-group, the species differs more in both morphology and cytology.  This suggests that the fusion leading to the reduced chromosome number occurred much earlier than those leading to C. staegeri and C. 'tigris'.

This species was placed in the subgenus Camptochironomus by Beyer (1941), but was not included in that subgenus by later workers.  Morphology and cytology described by Wülker et al. (1971).  Sublette and Sublette (1971) note that the only species that the adult male could be confused with is C. tentans, but this should also include C. pallidivittatus and C. vockerothi, the latter particularly since Rassmussen (1984) queried whether that species might be a hybrid between C. tentans and C. crassicaudatus.
The species can be bred in the laboratory (Hein and Schmulbach 1971; Frouz et al. 2002).