Species 2p. C. utahensis Malloch, 1915.

Adult redescribed by Townes (1945) and by Sublette in Wülker, Sublette & Martin (1991).

Pupa: Length 8.22-9.67 mm.  Cephalothorax brownish-black, papillose; abdomen pale, very weakly dark longitudinal stripes laterally; posterolateral spur and margin of anal lobe dark.  Cephalic tubercles relatively long and curved.  Hooks of tergum II pale, mean 90 (82-91); postero-lateral spur with 6 (4-8) appressed spines; fringe of anal lobe with 94 (88-100) flattened taeniae.

Fourth instar larva a medium sized bathophilus- or melanotus-type (i.e. with small lateral projections, up to 120 µm long, variable within and between populations); length 13-15.8 mm (fem); 10.6-14.3 mm (male); Ventral tubules about equal length, although anterior generally slightly longer (ant. 1.40-2.68; post. 1.20-2.64).  Postero-lateral tubule (TLt) and Ventral tubule lengths vary between populations: e.g. both are relatively longer at Klamath Falls than in California, and in California only 3 of 9 larvae had TLt up to 40 µm, while all larvae from Klamath Falls possessed TLt, varying from 40-200 (ave. 95) µm.  Anal tubules a single lobe, with some variability in length between populations, dorsal pair generally longer and varying from about 2-3.5 times longer than wide in California and South Dakota to 4-4.2 times longer than wide in Oregon.
Dark to very dark posterior 2/3 of gula region with V-shaped anterior margin, wider than the mentum width with the widest point anterior to the posterior margin of the head; pale frontoclypeus or slightly darkened (in California); and antennal pedicels characteristically darkened.
Oesophageal opening relatively small, about 58-71 µm wide and 3.3-3.5 times wider than deep.
Mentum (Fig. d) with somewhat rounded teeth; centre (c1) tooth relatively narrow with short parallel sides, c2 teeth well separated (type III, but can appear as IB if worn); 4th lateral reduced at least to the level of the 5th lateral (type II-III).
Ventromental plates (Fig. e) about 220-228 µm wide 3.3-4.1 times wider than deep; Inter Plate Distance about 0.38-0.45 of mentum width; with 38 (34-44) striae reaching about 2/3 to the anterior margin; VMR about 0.32 (0.27-0.30).  Pecten epipharyngis (Fig. a) with 11-15 relatively uniform, broader teeth (type B).
Premandible (Fig. b) with inner tooth relatively broad, about 3.2 (2.5-3.8) times wider than the slightly longer outer tooth, which narrows sharply along its length to a point.
Basal segment of antenna (Fig. c) about 30-40% of Ventral Head Length and about 2.8-3.97 times longer than wide, RO between 1/3 and 1/2 way up from base of segment; AR about 2.3 (1.8-2.6); A2/A1 about 0.21-0.28; segment lengths (micron) 137.5 : 32 : 7.5 : 12.5 : 7; i.e. A3 only slightly longer than A5.
Width between the antennal bases (170 (149-192) µm) and that between S4 setae (172 (154-187) µm) generally similar, but can vary in either direction.
Mandible with 3rd inner tooth usually partly separated, but sometimes well separated ( as Fig. f); but relatively pale (type II-IIIB); about 16 (11-20) furrows on outer surface at the base; Pecten mandibularis with 12.5 (11-14) taeniae; Mdt-Mat 28-33, MTR about 0.28-0.43.

Cytology:  4 polytene chromosomes with the thummi arm combination AB, CD, EF, G.
Centromeres partly heterochromatic, particularly for CD chromosome.
Arm G closely paired, without a nucleolus, but with a Balbiani ring (BR) towards one end, the position varying due to an inversion.  The end near the BR is almost square due to a constriction, while the other end is fanned.  Nucleolus in arm D.
Polymorphic in arms A, D, E, F and G.
The basic sequences (A1-G1) appear common to all populations, but the type and frequency of polymorphisms is variable and appears limited to particular areas.

utaA1:    1a-e, 7 - 4, 13 - 15, 3e - 2d, 9 - 8, 3f-i, 12 - 10, 2c - 1f, 16 - 19
utaA2:    approximately   1a-e, 7 - 4, 13 - 15, 3e-b, 9a-g, 2d - 3a, 8?-a, 3f-i, 12 - 10, 2c - 1f, 16 - 19.
utaB1:    Puff with distal dark bands (groups 7-8) near distal end of the arm, small BR in proximal third of arm.                    (Oreg.)
utaC1:    1-6b, 12b-15, 18d-17b, 6c-f, 7a-d, 16-17a, 6hg, 11d-12a, 11c-8, 18e-22
utaC2:    approximately   1, 14-12b, 6b-2, 15a-e, 18d-17b, 6c-f, 7a-d, 16-17a, 6hg, 11d-12a, 11c-8, 18e-22                        (Calif. & Oreg.)
utaC3:    approximately   1-2e, 3-2f, 4-6b, 12b-15, 18d-17b, 6c-f, 7a-d, 16-17a, 6hg, 11d-12a, 11c-8, 18e- 22                         (Calif.)
utaD1:    1-3e, 17b-13d, 12-13c, 4c-a, 10-9, 17c-19b, 11a-c, 3gf, 8-5, 19c-24
utaD2:    1-3e, 17b-13d, 19b-17c, 9-10, 4a-c, 13c-12, 11a-c, 3gf, 8-5, 19c-24                                                                            (Calif.)
utaD3:    large inversion, limits not defined                                                                                                                                  (Oreg.)
utaD4:     1, 15-17b, 3e-2, 14-13d, 12-13c, 4c-a, 10-9, 17c-19b, 11a-c, 3gf, 8-5, 19c-24                                                           (N. Mex.)
utaE1:    1 -3e, 5 - 7c, 12 - 10c, 3f - 4, 10b - 7d, 13a-g                                                                        ie. differs from aberratus by Inv 12-7d
utaE2:    Inversion of middle part of the arm                                                                                                                      (Silver Lake, Calif.)
utaF1:    1a-i, 9 - 2, 17 - 13c, 11 - 13b, 10d-a, 18 - 23
utaF2:    approximately   1a-i, 15c - 13c, 2 - 9, 15d - 17, 11 - 13b, 10d-a, 18 - 23                                                                   (Calif. & Oreg.)
                i.e. differs from F1 by two overlapping inversions 14-13c and 9-17.
utaG1:    Obvious BR about one third from centromere.
utaG2:    Invsion of about two thirds of the arm, taking the obvious BR to near the distal end.                                              (Calif. & Oreg.)

Found: Alberta - Elk Island; Lesser Slave Lake (Townes 1945).
            Arizona - Shultz Pass Tank and Lower Lake Mary, near Flagstaff, Coconino Co.
            California - 1.7 ml Benton Hot Springs (37.80°N, 118.50°W) and Convict Creek, Mono Co; nr Spring Valley Lake, Apple Valley, San
            Bernadino Co.; Alkali Lake, Antelope Valley, Kern Co. (Townes 1945); Antioch and West Pittsburg, Contra Costa Co.; Crowley Bishop,
            Inyo Co.; Litchfield and Westwood, Lassen Co.; Lancaster, Los Angeles Co. Stranghold, Modoc Co.; Lake Davis, Plumas Co.;
            Sheepy Creek, Siskiyou Co. (Wülker et al. 1991).
            Colorado - Fort Collins (Townes 1945).
            Minnesota - Sand Lake (Townes 1945).
            Montana - 2 ml s. Ronan, Lake Co.
            Nevada - Reno and Wells (Townes 1945).
            New Mexico - Mineral Springs, Taylor Springs, Colfax Co.; Eagle Nest Lake (36.55°N, 105.25°W), Miami Lake, Stubblefield Lake,
            Springer Lake, all Colfax Co.; Upper Abbott Lake(36.25°N, 104.33°W), Harding Co.
            Oregon - Upper Klamath Lake (42.47°N,121.95°W), 1 ml Williamson River, Klamath Co.
            North Dakota - Dead Colt Creek Dam; Crystal Springs, Kidder Co. (Wülker et al. 1991)
            South Dakota - Wagner, Platte Lake, and Lake Francis Case, Charles Mix Co. (Wülker et al. 1991).
            Utah - Kaysville (Type); Bear River Bay; Great Salt Lake; Honeyville; Magna; and Plain City (Townes 1945); Goshen, Utah Co.;
            Sevier Bridge Res. and 6 ml W. Smithfield, Sanpete Co. (Wülker et al. 1991).

            Shallows of lakes or other pools, particularly where much algal growth, in western and central North America.

Morphology and cytology described by Wülker, Sublette & Martin (1991), which corrects a minor error in the arm E sequence in Martin, Sublette, Sublette (1979).  A photograph of the karyotype was also published in Schaller & English (1976) and Kiknadze et al. (2010).  The cytology places C. utahensis as a member of the karyosystematically defined (but not the morphologically defined) "decorus-group".
The adult male is recognized by the dark color, heavy fore-tarsal beard, broad anal point and the almost capitate Inferior volsella.  Smaller specimens can be similar to larger specimens of C. atrella but are darker and have a heavier beard (Townes 1945). Known as the "Klamath midge" because of the large numbers causing nuisance in the vicinity of the Klamath lakes.
The larvae are quite variable between localities and, taken along with the apparent clines of inversion polymorphism (Wülker et al. 1991), and possible differences in the SVO, raises the question as to whether there may be incipient species involved.