Species a.  C. bifurcatus immatures

Fourth instar larva:  small to moderate size, length 12.3 (10-15); (female 10.2-13.8 mm, 16), (male 11.3-13.4 mm, 4) (male); essentially of the fluviatalis- or 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 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 half to 2/3 extending beyond the width of the mentum, usually higher at the outer edges and widest about the midpoint, frontoclypeus pale or only slightly darkened (in Michigan larvae).  Oesophageal opening about 50.5-73 µm wide, and 2-4.5 times longer than wide (higher values apparently due to flattening in preparation).
Mentum (Fig. d) with pointed teeth, c2 teeth sommetimes only partly separated from the c1 tooth (type IB or III), but may also be type III; 4th laterals reduced about to level of 5th laterals (type II).
Ventromentum (Fig. e) about 185-220 µm wide and 3.30-3.69 times 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 (0.28-0.45) 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 3-5 times the width of the outer tooth, which narrows markedly to a sharp point.
Antenna (Fig. b) 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 about 2.05 (1.68-2.76); A4/A3 about 1.5-2; A3 shorter than A4 (A4/A3 abt. 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 occasionally 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).

The pupa is typical of most of the species in the C. decorus-group, in lacking the secondary tubercle on the cephalic tubercles found in C. decorus itself.
Length 6.45-8.08, mean 7.56 mm (11).  Cephalothorax mostly dark; frontal tubercles black, remainder of frontal apotome pale; abdomen pale with faint lateral vertical stripes on either 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.
Swim fin with 71-93 taeniform setae.

Spur of pupa from same egg mass as the Holotype

The pupa is very similar to that of its sister-species C. 'proulxi', although overall apparently slightly larger.  Unfortunately the available data took no note of the sex of the exuviae, but the largest specimens are larger than the largest females of C. 'proulxi', the number of recurved hooks on segment II is higher (78-118 c.f. about 62-84) and there may be more spines on the spur (up to 6 c.f. an occasional 3 in C. 'proulxi').

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 proposed name.  The whole arm may be unpaired, and this may be due to the presence of inversion polymorphism.  No nucleoli in the long chromosomes.  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
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.