Species a.  C. bifurcatus Wülker et al., 2009

A member of the C. decorus group.
Also C. species B1 = C. decorus-gr sp.1 of Butler et al. 1995.

In BOLD Bin: BOLD:AAG5453 (Gp. 1)

Adult:The adults and other life stages were described by Wülker et al. (2009).  However these descriptions are probably a mixture of specimens of C. bifurcatus and C. 'proulxi', so need to be revised.

Male:
The adult male is a typical member of the C. decorus-group.  Rather similar to those of C. maturus Johannsen in coloration and in the darkened superior volsella of the male genitalia, but the superior volsella is shorter and darker than that of C. decorus.
Coloration: Head and thorax light to dark brown, postnotum blackish, scutellum paler, median and lateral vittae weakly separated by lighter colour; abdomen strongly vittate, with the basal dark bands occupying half or more of each tergum, except on tergum VI where the dark marking is more saddle-shaped, as C. decorus; legs pale yellowish brown.

Abdominal pattern of C. bifurcatus from Wülker et al. 2009


Head: AR 4.14 (3.33-4.21); temporal setae 32 (29-32); clypeus about 0.84 width of antennal pedicel; clypeal setae 27-40; frontal tubercle length 42-86 µm; palp proportions II-V (µm): 62: 226: 273: 383.
Thoracic setae - Acrostichals abt. 16; dorsocentral 27, mostly in 2 rows; prealar 6; supraalar 1; scutellar 30, with 15 in posterior row, rest scattered anteriorly.
Wing length 2.87-3.95 mm; width 0.92-1.00 mm; VR 0.98.
Legs: LRI 1.58; LRII 0.62; LRIII 0.77; BR 3.0.
Leg measurements and proportions (micron)
 
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
BR
PI
1190
1190
-
-
-
-
-
1.51-1.68-
1.0
2.31-3.57
PII
1385
1150
730
385
230
190
150
0.61-0.66
1.18-1.20
-
PIII
1385
1190
1150
615
405
365
-
0.71-0.80
1.0-1.16
-

Some measurements of a confirmed specimen can be provided from a male (see below) from a photograph in the BOLD database; and for the hypopygium, from an adult from the same egg mass as the Holotype:

Basal dark band at anterior of abdominal tergites, broader at mid-line and becoming more extensive until segs. VI-IX are almost completely dark.Wing length 3.8 for certain–4.1 mm, width 0.9-1.0 mm.



Male terminalia of C. bifurcatus.
Adult from the same egg mass as the Holotype.


A typical C. decorus-type hypopygium, with Superior vosella similar to that of C. maturus.  Tergite IX with 12 (8-16) setae in separate ppale patches.  Superior volsella dark, of D-type of Strenzke (1959); Inferior volsella reaching just beyond the end of the anal point and to about the midpoint of the Gonostylus, which is moderately swollen and narrows sharply over posterior third.





Female: - some data from photographs on BOLD


Female BIOUG03114-A06 from BOLD database



Coloration basically similar to male; abdomen with dark band on basal half of segment.
Legs pale with some darkening at knees and on apical part of tibia, particularly on fore legs.
Wing length about 2.25-4.7 mm; width about 1.14, VR abt 1.05.

Leg proportions (approx.) (micron):

 
Fe
Ti
Ta1
Ta2
Ta3
Ta4
Ta5
LR
F/T
BR
PI
1445
1310
-
-
-
-
-
-
1.10
-
PII
1500
1630?
-
-
-
-
-
-
0.92
-
PIII
1635
1765
1290
710
400
-
-
0.73
0.97
-



Pupa is typical of most of the species in the C. decorus-group, in lacking the frontal warts on the frontal apotome found in C. decorus itself.
Length 7.56 (6.45-8.08) mm (11).
Cephalothorax mostly dark; frontal tubercles black, remainder of frontal apotome pale; abdomen pale with faint lateral vertical stripes on either side of TI; TII-TIV with heavy lateral dark, vertical stripes; TVI, TVII with much weaker lateral stripe, reaching only about halfway to the posterior margin of each tergum; lateral margin of V-VIII darker, heaviest on TVIII, which grades into the dark posterolateral spur; lateral margins of swim fin darkened.
Cephalothoracic tubercles weak; prealar tubercle elongate, not strongly produced.
Abdominal shagreen moderately developed occupying slightly more than the apical half of TII; TIII-TVI with a quadrate shagreen patch which is slightly expanded laterally on TIII-TV and less so on TVI; TVII with a weak patch on each side near the base; TVIII with heavier shagreen than VII.
TII with a continuous row of 78-118 posterior hooks.
Caudolateral spur normally with about 2–3 apical spines, but varying from 1 to 6.  It differs from C. maturus in the usually higher number of spines.
Fringe of anal lobe with 71-93 taeniform setae.

a, c-e - Pupal characters of C. bifurcatus.  b. Frontal apotome of C. decorus (sp. 3a) showing the secondary tubercles not found in other species of the C. decorus-group.  d. Spur from pupa from same egg mass as the Holotype  From Wuelker et al. (2009).





Fourth instar larva  small to moderate size, length 12.3 (10-15)(33), (fem.11.4-13.8), (male 11.4-11.8) mm; essentially of the bathophilus-type but sometimes a melanotus-type with some development of posterolateral tubules in Canadian samples (0-160 µm).  The presence and absence of lateral tubules can be seen even in offspring from a single egg mass, as in the type egg mass larvae, suggesting it is genetic in origin.Ventral tubules essentially the same length although the anterior pair have a slightly higher mean length (ant. 1.41 (0.87–2.28), post. 1.35 (0.87–2.04) mm); those of mid-west larvae are of 'fluviatilis' type (this may be a characteristic of larvae from deeper waters).
Anal tubules with median constriction, dorsal and ventral pair essentially the same size (354-620 µm long, and 2.5-6.2 times longer than wide).
Gular region dark on posterior third to half, frontoclypeus pale or only slightly darkened.
Mentum (Fig. d) with pointed teeth, c2 teeth sometimes only partly separated from the relatively tall c1 tooth (type III); 4th laterals reduced at least halfway to the level of 5th laterals (type I-II).
Ventromentum (Fig. e) about 185-220 µm wide and 3.30-3.69 wider than deep; 0.97-1.19 times the width of the mentum; with about 35.24 (30-49) striae, and separated by a third or more (0.32-0.43) of the mentum width, VMR about 0.22-0.35.  Pecten epipharyngis (Fig. a) with about 12.3 (11-15) generally sharp, even teeth (type B).  Premandible (Fig. b) with moderately broad inner tooth about 2.5-4 times the width of the outer, which narrows markedly along its length.
Antenna (Fig. c) relatively short, about 30-40% of ventral head length; basal segment about 2.6-4.1 times as long as wide; ring organ a third to almost half way up (0.31-0.47) segment 1; segment proportions (microns) 112 : 29 : 7 : 12 : 6.5 ; AR 2.05 (1.68-2.76); A3 shorter than A4 (A4/A3 about 1.4-2.2), and sub-equal or slightly longer than A5 – 1.06 (0.82-1.37).
Distance between the antennal bases is equally greater or smaller than the distance between the S4 setae, which are separated by about 80-90% of the FC width at that point.  S5 setae usually about level with or slightly anterior to the nearby RO.
Mandible (Fig. f) with the third inner tooth partially separated and pale or slightly darkened (type IA-IIB), about 19.1 (18-22) furrows on outer surface near base; Pecten mandibularis with 11.7 (10-13) taeniae; Mdt-Mat 26.7 (20-33), MTR 0.33 (0.27-0.39).

Cytology:  4 polytene chromosomes with thummi arm combination AB, CD, EF, G.
Arm G usually at least partially unpaired with a terminal nucleolus and Balbiani ring.  The nucleolar end is always unpaired, giving the forked appearance referred to in the name.  The whole arm may be unpaired, and this may be due to the presence of inversion polymorphism.  No nucleoli in the long chromosomes.  Puff with distal dark bands usually developed near center of arm B. Polymorphic in arms A, B, C, D, E, F and G (at least band polymorphism, but also an inversion).  At least three new heterozygous inversions have been identified since the published map of Wülker et al. (2009).

bifA1:    1a-e, 14 - 15, 7b - 4c, 13a-f, 8d - 9, 2d - 3e, 17h-a, 3f-i, 12 - 10, 2c - 1f, 8c - 7c, 4ab, 16a-d, 18 - 19
bifA2:    1a-e, 14 - 15, 7b - 4c, 13a-f, 8d - 9, 2d - 3e, 16d-a, 4ba, 7c - 8c, 1f - 2c, 10 - 12, 3i-f, 17 - 19
bifA3:    1a-e, 14a-g, 3e - 2d, 9 - 8d, 13f-a, 4c - 7b, 15e-a, 14ih, 17h-a 3f-i, 12 - 10, 2c - 1f, 8c - 7c, 4ab, 16a-d, 18 - 19
bifA4:    1a-e, 14a-g, 3e - 2d, 9 - 8d, 13f-a, 4c - 7b, 15e-a, 14ih 4ba, 7c - 8c, 1f - 2c, 10 - 12, 3i-f, 17a-h 16a-d, 18 - 19
bifB1:    Large puff (group 7) near the middle of the arm.
bifB2:    Puff in more distal position
bifC1:    1 - 6b, 12b - 15, 8 - 11c, 12a - 11d, 6gh, 17a - 16, 7d-a, 6f-c, 17b - 22                              as C1 of blaylocki
bifC2:    1 - 4h, 15 - 12c, 6b-4i, 8 - 11c, 12a - 11d, 6gh, 17a - 16, 7d-a, 6f-c, 17b - 22
bifD1:    1 - 3e, 18d - 13d, 7e - 10, 4a-c, 13c - 11, 3gf 18e-g, 7d - 5, 19 - 24
bifD2:    1 - 3e, 10 - 7e, 13d - 18d, 4a-c, 13c - 11, 3gf 18e-g, 7d - 5, 19 - 24
bifD3: approx 1 - 3e, 10 - 9, 16 - 13d, 7e - 8, 17 - 18d, 4a-c, 13c - 11, 3gf 18e-g, 7d - 5, 19 - 24
bifE1:    1 - 3e, 5 - 10b, 4 - 3f, 10c - 13;    i.e. as aberratus, sp. 3p.
bifE2:    1 - 3a, 10e-c, 3f - 4, 10b - 5, 3e-b, 11 - 13
bifF1:    1, 9 - 7, 14 - 17, 11e - 13, 11d - 10, 2 - 6, 18 - 23
bifF2:    approx.    1, 14 - 17, 19 - 18, 6 - 2, 10 - 11d, 13b - 11e, 17 - 14, 20 - 23
bifF3:    approx.    1, 9 - 7, 14 - 17, 11e, 5 - 2, 10 - 11d, 13 - 12, 6, 18 - 23
bifG1:    terminal nucleolus and usually a large median BR and a smaller almost terminal one.
bifG2:    a small inversion around the median BR (may be C 'proulxi').

Found: Alberta – Elk Island Nat. Pk. (BOLD database)
            Nova Scotia – Point Pleasant Park, Halifax (44.623°N, 63.569°W) (from GenBank).
            Ontario – Lac Deschêne (45.37°N, 75.85°W) (Type locality); Arboretum (45.40°N, 75.87°W), both Ottawa; Copanspin Farm, Dunrobin
            (45.75°N, 75.87°W); 0.5 ml. Dunrobin (45.40°N; 75.87°W); South March (45.40°N, 75.87°W), all Carleton Co.; Costello Creek,
            Algonquin Provincial Park, Nipissing Co. (abt. 45.58°N, 78.70°W); Georgian Bay Islands N.P. (44.7418°N, 79.8501°W)(BOLD);
            Catholic Central H.S. (42.9869°N, 81.239°W) and Oakridge Secondary School (42.978°N, 81.312°W), both London (BOLD).
            Quebec – L. Adéline (48.20°N, 79.17°W); L. D'Allembert (48.38°N, 79.02°W), L. Arnoux (48.25°N, 79.33°W), L. St. Joseph
            (46.8°N, 71.63°W), L. Duprat, (48.33°N, 79.12°W) and L. Opasateca (48.17°N, 79.33°W), (Proulx et al.).
            Massachusetts – Lake Pleasant (43.56°N, 72.51°W), nr. Montague, Franklin Co.
            Minnesota – Turtle Lake, Becker Co. (M.G. Butler).

Localities not clearly identified as C. bifurcatus or C. 'proulxi':
            Manitoba – Lake Winnipeg (Sæther 2012)
            New Brunswick – Kouchibouguac Natl. Pk. (48.858°N, 64.975°W).
            Ontario – Bear Creek, Carlsbad Springs (45.37°N, 75.47°W), Carleton Co.; Algonquin Provincial Park (abt 45.58°N, 78.70°W),
            Nipissing Co.
            Quebec – Brewery Creek, Hull (45.43°N, 75.73°W), Gatineau.
            Kansas – Lone Star Lake (38.83°N, 95.38°W), Douglas Co.
            Michigan – Lake Michigan, Epoufette (46.05°N, 85.17°W).
            Minnesota– Anderson Lake, Clearwater Co.; Bad Axe Lake, Hubbard Co. (M.G. Butler).

Creeks, pools, shallows to profundal of lakes.   Occurs with C. decorus (sp. 3a) in some localities  At least where this occurs, the larvae of the two species can be separated by the greater region of gula darkening and the longer anal tubules of C. decorus.
In common with many widely distributed species, many characters are variable in different geographic areas but, as noted above, the egg mass data indicates that there are genetic differences even within localities.

All life stages (except female) and the salivary gland chromosomes described by Wuelker et al. (2009) (but see note above).  Some information on arm F given in Fig. 3 of Martin (1979) and a photograph of the chromosomes in Butler et al. (1995) as C. decorus-gr. species 1.

DNA analysis: Sequences for the mitochondrial COI and the nuclear gb2Β genes are available.The data of (Proulx et al. 2013) suggested that the species may comprise two closely related components.
Further data supports this view and is discussed more fully here.

For clarification of which is C. bifurcatus, information on specimens from the same egg mass as the Holotype is provided.

See also C. decorus Joh.,  (see also C. decorus Rothfels and Fairlie),  C. sp. nr. bifurcatus,  C. sp. b,   C. sp. c,   C. sp. j,  C. sp. 2a,   C. 'proulxi',   C. 'butleri",   C. sp. 3h,   C. sp. 3i,   C. sp. 3j,   C. harpi,   C. blaylocki,   C. mozleyi,   C. winnelli,   C. sp. 4l.

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Modified: 3 October 2021
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