Species p.  C. plumosus (Linn., 1758)

Adult essentially similar to C. entis.  Shobanov shows some differences exist in Palearctic specimens, but these have not been confirmed in the Nearctic.  Townes (1945) description probably includes C. entis, but is likely correct in gross details, given the two species are so similar.  No description of the adults or pupae of the Nearctic specimens appears to have been published subsequent to the identification of C. entis, so the data for Palearctic specimens from Shobanov (2005) will be used.

About 13 setae on TIX, mostly in individual clear spots; Superior volsella possibly closest to E(i) of Strenzke (1959); inferior volsella reaches only to about the end of the anal point and about half-way along the length of the gonostylus which narrows more gently over posterior third to half.  A comparison with Shobanov's figures suggests that the illustration of the hypopygium in Townes (1945) (below) is that of C. plumosus.

Male hypopygium identified as C. plumosus from South Dakota (left) and from Townes 1945 (left)

Female:
Townes (1945) and some others simply state: "Similar to male except for the usual sexual differences".  However, Johannsen (1926) in his notes on C. ferrugeovittatus, an agreed synonym of C. plumosus, states that the setae on fore Ta1 are much shorter than the diameter of the segment, i.e. BR less than 1.
Specimens from BOLD have wing length 7.3 mm; LR 1.21-1.25.
Rodova (1978) provided some information (in Russian) for European specimens and illustrated some characters.  Cercus roughly oval with the longer axis in the dorsal/ventral orientation with the ventral margin including the bulge seen in other species.

Pupa:(from Langton & Visser (2003) (Palearctic specimens):
Length 16.5 (14.3-19.4) mm.  Exuvia golden to golden brown, rarely brown.
Cephalic tubercles 213 x 177 - 275-225 µm; frontal setae87-110 µm.  Thoracic base 250x100 – 370-x155 µm.
Hook row of segment II entire, covering 0.54-0.61 of segment width; 63-113 hooks.
Armament of TII-VI not strongly waisted, posterior transverse band not increasing in length to TVI; usually reduced on TVI.
Spur of segmant VIII with 12-26 elongate teeth; fringe of anal lobe with 211 (82-285) taeniae.

Fourth instar larva a large (13.7-29.9 mm: fem. 27.2-29.9; male 20.3-25.4) semireductus- or plumosus-type, anterior ventral tubules often with a flexure in basal half (Butler, unpubl.), and often longer than posterior pair (ant. 0.4-2.07 mm; post. 0.4-1.29 mm), but in New Mexico specimens the VT are longer and the posterior pair are nearly equal, or may be longer.  Lateral tubules variable, from 90-550 µm in length.  Anal tubules quite long (759-911 µm) and about 2.2-3.0 times longer than wide (ventral pair often narrower than dorsal pair).
Gular region dark covering most of the region, but often with a slightly scalloped anterior margin, frontoclypeus pale.

Mentum with pointed teeth and fourth laterals hardly reduced (type I);  c1 tooth relatively narrow, c2 teeth well separated (type III or sometimes tending to type IIA, particularly if worn).
Ventromentum about 3.9-4.4 times wider than deep, with a slightly jagged edge, particularly near the centre, due to the presence of protruding outer hooks (Shobanov (1989) notes that these hooks have the shape of an isosceles triangle), striae reaching to margin.  VMR difficult to measure because of the striae in the anterior region, 0.28 (0.23-0.37); separated by about 1/3 of mentum width; and 1.04 (1.0-1.09) times the mentum width.  Pecten epipharyngis with about 12-20 broad, normally sharp, teeth (type B); epipharyngeal opening about 3.56 (2.2-5.5) times longer than wide.
Antenna with relatively long narrow basal segment, about 3.7 (3.1-4.2) times as long as wide (lower figures, e.g. 2.62, may be obtained where the mandibles have not been dissected off, probably due to increased squashing of the antennae), RO near middle of the segment (0.32-0.54); AR 2.08-3.47; relative lengths of segments (µm) 167 : 38 : 11 : 15 : 9, but segment 3 may be only as long as segment 5.
Distance between the antennal bases about the same as that between the S4 setae, but can vary in either direction.  S4 setae about 238-278 µm apart, about 0.73-0.84 of frontoclypeus width.
Mandible with third inner tooth well developed and darkened (type IIIC), with about 28-34 furrows on the outer surface near base and 11-14 taeniae in the pecten mandibularis.

Cytology: 4 relatively short polytene chromosomes with the thummi arm combination AB, CD, EF, G.  Banding pattern often unclear.
Arm G usually unpaired, or paired only in the region of the large virtually terminal nucleolus - often with a constriction just before the nucleolus; at least one Balbiani ring (BR) near the other end.
No nucleoli in other chromosomes but a BR often developed in arm B, generally near the 4 characteristic bands near the centromere, but sometimes towards the end of the arm due to polymorphism.
Arm A generally with sequence n'pluA9, but often with h'pluA2, possibly latitude or depth dependent.
Polymorphism in arms A, B, D, and E including pericentric inversion E4/F4.  B chromosomes found in two populations.

h'pluA2:    1 - 2c, 10 - 12a, 13ba, 4a-c, 2g-d, 9 - 4d, 2h - 3, 12c-b, 13c - 14f, 15a - 14g, 15b - 19
n'pluA9:    1 - 2a, 17 - 13c, 12bc, 3 - 2h, 4d - 9, 2d-g, 4c-a, 13ab, 12a - 10, 2cb, 18 - 19
n'pluA10:    1a-e, 3e-a, 2k-h, 4d-9, 2d-g, 4c-a, 13ab, 12a-10a, 2c-a, 1k-f, 3f-i, 12cb. 13c-14f, 15a-14g, 15b-19
n'pluA11:    1-2a, 17-15b, 14g-15a, 14f-13c, 12bc, 3-2h, 4d-9, 2d-g, 4cb, 19d-18, 2bc, 10-12a, 13ba, 4a, 19ef                     from n'pluA9
h'pluB1:    1 - 4c, 20c - 23a, 20b - 19, 15 - 17, 6d - 4d, 6e - 8b, u, 19a - 18, 8c-13, 23b - 28
                  BR proximal, near the 4 characteristic bands; puff in group 7 not developed.
h'pluB2:    approx. 1 - 4c, 20c - 23a, 20ba, u, 13 - 8c, 18 - 19a, 8b - 6e, 4d - 6, 17 - 15, 19a-i, 23b - 28
                  BR distal due to large inversion of h'B1 (heterozygous only)
n'pluB4:    BR proximal, inversion of region 5-10 (heterozygous only)
n'pluB5:    BR about middle of arm due to complex inversion (heterozygous only)
h'pluC2:    1-2c, 6c-f, 7a-d, 16-17a, 6hg, 11d-12, 4-6b, 11c-8, 15-13, 3-2d, 17b-22
h'pluD2:    1-3, 10b-e, 4-7, 18a-d, 8-10a, 13a-11, 13b-17, 18e-24
n'pluD6:    1-3, 10b-e, 4-7, 18g-e, 17-13b, 11-13a, 10a-8, 18d-a, 19-24
n'pluD7:    1-3, 10b-e, 4-7, 15d-13b, 11-13a, 10a-8, 18d-a, 15e-17, 18e-24
n'pluD8:    1-3, 10b-e, 4-7, 18ab, 11-13a, 10a-8, 18dc, 13b-17, 18e-24
n'pluD9:    1-3, 10b-e, 4-7, 18ab, 9-8, 18dc, 10a, 13a-11, 13b-17, 18e-24
n'pluD10:    1a-d, 2f - 1e, 2gh, 3a-g, 10b-e, 4 - 7, 18a-d, 8a - 10a, 13a - 11a, 13b - 17, 18e-24
n'pluD11:    1 - 3, 10b-e, 4ab, 18ba, 7 - 4c, 18cd, 8 - 10a, 13a - 11, 13b - 17, 18e - 24
p'pluE1:    1 - 3a, 4c - 10b, 3e-b, 4b -3f, 10c - 13
h'pluE2:    1 - 3e, 10b - 3f, 10c - 13
n'pluE4:    1 - 3c, 4c - 10b, 3ed, 4b - 3f, 10c - 13 [F20d - 23]                                  (Kiknadze et al. 2016)
h'pluF1:    1a-d, 6 - 1e, 7 - 10b, 18ed, 17 - 11, 18a-c, 10dc, 19 - 23
n'pluF4:    1a-d, 6 - 1e, 7 - 10b, 18ed, 17 - 11, 18a-c, 10dc, 19a - 20c -/- armE
h'pluG1:    as Palearctic populations

Found: Numerous lakes in Canada and U.S.A.:
            Alberta - Amisk Lake (54.59°N, 112.63°W) (Kiknadze et al. 2016) and South Baptiste Lake (54.72°N, 113.57°W) both Athabasca Co.
            British Columbia - Near Opposite Crescent, Bechers Prairie, Cariboo and Chilcotin Parklands (about 52.13°N, 122.14°W) (Cannings);.
            Manitoba - Delta Marsh Beach (50.20°N, 98.20°W), Portage la Prairie (Kiknadze et al. 2016); Lake Winnipeg (about 52.10°N, 97.25°W)
            (from figures of Sæther 2012).
            Ontario - Arboretum (45.38°N, 75.70°W), Ottawa; Bay of Quinte, Belleville (44.15°N, 77.25°W) (O. Johannsen); Milhaven Bay,
            Lake Ontario (44.20°N, 76.75°W) (P. Rueffel); White Lake, 3 Mile Bay (D.R.Oliver); Kelly Lake 46.45°N, 81.07°W), Sudbury
            (Proulx et al. 2013).
            Quebec - Lake Saint Augustin (46.75°N, 71.40°W), Quebec City; Lake D’Alembert (48.38°N, 79.03°W), Lake Duprat
            (48.33°N, 79.12°W), Lake Fortune (48.18°N, 79.32°W), Lake Kinojévis 48.13°N, 78.90°W), Lake Marlon (48.27°N, 79.07°W),
            Lake Osisko (48.27°N, 79.00°W), Lake Pelletier (48.22°N, 79.05°W), and Lake Rouyn (48.17°N, 78.95°W), all Rouyn-Noranda
            (Proulx et al. 2013).
            Saskatchewan - Lake Waskesiu (53.92°N, 106.08°W), Prince Albert National Park.
            Alabama - Farm pond, Auburn (32.58°N, 85.48°W), Lee Co.
            California - Clear Lake; Lake Merced (37.72°N, 122.495°W), San Francisco.
            Colorado - Crawford Lake (38.40°N, 107.35°W), Delta Co.; Kettering Reservoir (39.57°N, 105.02°W)(1641m), Broomfield Co. and
            Littleton (39.629°N, 105.01°W)(1631 m), Jefferson Co. (Kiknadze et al. 2016); Miramonte Lake (37.58°N, 108,20°W), San Miguel Co.;
            Vega Reservoir (39.13°N, 107.47°W), Mesa Co.
            Georgia - Lagos Pond (33.97°N, 83.33°W), Athens, Clarke Co.
            Indiana - Crooked Lake(41.68°N, 85.05°W), Angola, Stueben Co.; Crooked Lake (41.44°N, 85.80°W), and Sylvan Lake
            (41.50°N, 85.35°W), both Noble Co.; Manitou Lake (41.06°N, 86.19°W), Fulton Co.; Shafer Lake (40.83°N, 86.80°W), White Co.
            Kentucky - Lake, Campbell Co.(J.E. Sublette);
            Massachusetts - East Longmeadow Pond (42.07°N, 72.51°W)(Kiknadze et al. 2016).
            Michigan - Saginaw Bay (43.45°N, 83.67°W), Lake Huron, Bay Co.
            Minnesota - Anderson Lake (47.29°N, 95.25°W); Lake Itasca (47.23°N, 95.21°W), Clearwater Co.; (R. Hellenthal); Lake Christina
           (46.08°N, 95.75°W), Douglas Co.; Spearhead Lake (47.37°N, 94.96°W), Hubbard Co. (Kiknadze et al. 2016).
            New Mexico - Eagle Nest Lake (36.55°N, 105.25°W), Colfax Co.; Upper Abbot Lake (36.25°N, 104.33°W), and
            Lower Abbot Lake (36.25°N, 104.33°W), both Harding Co.
            North Dakota - Blacktail Dam (48.26°N, 103.44°W), Williams Co.; Brewers Lake (47.15°N, 97.46°W), Cass Co.; Dead Colt Creek Dam
            (36.26°N, 97.41°W), and McVille Dam (47.77°N, 98.18°W), both Ransom Co. (Kiknadze et al. 2016); Fordville Dam (48.18°N,
            97.77°W), and Larimore Dam(47.93°N, 97.60°W), both Grand Forks Co.; Fullers Lake (47.19°N, 97.46°W), and South Golden Lake
            (47.31°N, 97.50°W), both Steele Co. (Kiknadze et al. 2016); Red Willow Lake (47.88°N, 98.40°W), Griggs Co.; Silver Lake
            (46.02°N; 97.57°W), Sargent Co. Warsing Dam (47.83°N, 99.12°W), Eddy Co.; White Earth Dam (48.45°N, 102.74°W), Mountrail Co.;
            Williams Lake (47.06°N, 99,40°W), Kidder Co. and Wilson Dam (47.06°N, 99.40°W), Dickey Co. (Kiknadze et al. 2016).
            Ohio - (Bolton 2012)
            Oklahoma - University of Oklahoma Biological Station (33.89°N, 96.83°W), Willis, Marshall Co.
            South Dakota - Lake Kampeska (44.93°W, 97.21°W), Codington Co. (J. Hartung); Burke Lake (43.11°N, 90.17°W), Gregory Co.
            (Kiknadze et al.)
            Wisconsin - Allequaush Lake (46.04°N, 89.62°W) and Mendota Lake (43.08°N, 89.39°W) (Kiknadze et al. 2016);
            East Horsehead Lake (45.70°N, 89.62°W), Onieda Co.(W.L.Hilsenhoff); Grand Portage Lake (46.10°N, 90.80°W), Iron Co.
            (W.L.Hilsenhoff); Green Lake (43.72°N, 89.00°W), and Little Green Lake(43.44°N, 80.59°W), both Green Lake Co.;
            Lake Kengonsa (42.977°N, 89.205°W), and Mendota Lake (43.08°N, 89.39°W), Lake Wingra (43.05°N, 89.42°W), and Murphy's Creek
            (43.05°N, 89.42°W), Madison, all Dane Co.; Lake Koshkonong (42.83°N, 89.00°W), Rock Co.; Lake Onalaska (43.87°N, 91.31°W),
            La Crosse Co. (J. Kawatski); Dane Co.; Pepin Lake (44.50°N, 92.30°W), Pepin Co; Pine Lake (45.68°N, 89.40°W), Oneida Co.;
            Pleasant Lake (42.79°N, 88.55°W), Walworth Co.(W.L.Hilsenhoff); Yellow Lake (45.55°N, 92.24°W), Burnett Co. (J. E. Sublette).
            Many localities from Butler et al. (1998b).

            Lakes up to considerable depths (up to 23 m).

Aside from the claim that C. vancouveri is a synonym, other workers (e.g.Hilsenhoff and Narf 1968) have suggested the existence of more than one species on ecological grounds.  The broad range of some measurements, along with the tendency for extreme specimens for one measurement to be near one or other extreme for other measurements, but not related to north/south distribution, would also be consistent with presence of two forms.
Cytological studies indicate the presence of C. entis, separated in part by differences in polymorphism and location of Balbiani rings.  The two species are often found in the same lake.  The form with 2 generations per year in general has better quality chromosomes.
It is also claimed that C. balatonicus and C. muratenis occur in Alberta, but this has not been confirmed.
The cytology of North American C. plumosus has been described by Butler et al. (1999, 2000), arm A revised by Golygina and Kiknadze (2008), with comparison of North American and Palearctic sequences by Kiknadze et al;. 2016.
Kiknadze et al. (1991) describe the outer hooks on the anterior margin of the ventromentum as being shorter and blunter than those of C. entis in Palearctic populations, but does not seem to apply in North America - besides being very difficult to see.  Although the ventral tubules are generally longer than those of C. entis, and where the two species occurred together at Lake Itasca, MN, they could be accurately separated on this character, there is considerable overlap and it can only be reliably used if over 1 mm in length.  Shobanov (1989) notes that the basal antennal segment of C. plumosus (abt 167 µm) is shorter than that of C. entis (abt 210 µm), so the other segments are relatively longer by comparison (100:23:7:9:5 cf. 100:18.5:5:7:4), while C. vancouveri has relatively shorter segments III, IV and V (100:21:4:6:3).

Molecular: C. plumosus and C. entis cannot be separated on the basis of the DNA "barcode" sequence of COI, but can be separated by the sequence of the globin gene gb2β (Guryev and Blinov 2002).