Species b. C. decorus group

Adult: The adult male is a typical member of the C. decorus-group.  The gonostylus is relatively short and stout compared to those of C. bifurcatus or C. blaylocki.  The superior volsella shows similarities to that of C. blaylocki.


Male terminalia of C. species b.
Note relatively short gonostylus, and the superior volsella similar to that of C. blaylocki.

Pupa: Caudolateral spur of segment VIII (below) with about 5 spines along the outer margin.

Larva of the plumosus-type with long ventral tubules, posterior pair normally longer (anterior 1.6 - 2.3 mm; posterior 1.9 - 2.8 mm).  Length, female 14.4 - 17.2 mm; male 12.0 - 15.3 mm.  Lateral projections about 170 - 360 µm.  Anal tubules relatively long, about 4.0 - 4.4 times longer than wide; with a median constriction, length about 550 - 700 micron, ventral pair may be narrower.

Gular region darkened, frontoclypeus normally darkened, occasionally pale.

Mentum width about half the ventral head length; with slightly rounded teeth, c2 teeth of centre trifid tooth well seperated (type III); fourth laterals not reduced (type I).
Ventromental plates separated by about one third of the mentum width, with about 44 - 47 striae; VMR about 3.2, increasing towards midline.  Pecten epipharyngis with about 14 teeth.
Premandible with outer tooth probably longer, but often broken or worn to about equal length, inner tooth about twice the width of the outer.
Antenna with basal segment about 3.6 times as long as wide; AR about 2.27 - 2.40; Ring organ just less than halfway up A1; A3 just shorter than A4, and just longer than A5.
Distance between antennal bases sometimes shorter, and sometimes about equal to width between S4 setae (see figure above).
Mandible about 240 - 250 mm long, with 3rd inner tooth relatively darkened, but not well separated (type IIB-C), with about 14 furrows on the outer surface at the base.

Cytology: 4 polytene chromosomes with thummi arm combination AB, CD, EF, G.
Arm G normally paired with subterminal nucleolus and Balbiani ring about one third from other end.  No other nucleoli.
Polymorphic in arms A, B, D, E & F.

Arm A1:    1a-e, 4d-a, 13-15, 3e-2d, 9-8, 5-7, 16d-a, 1f-2c, 10-12, 3i-f, 17-19                (Wülker)
Arm A2:    approx.  1a-e, 4d, 10a-e, 2c-1f, 16d-a, 7-5, 8-9, 2d-3a, 15-13, 4a-c, 11-12, 3i-f, 17-19
Arm B1:    Puff with proximal dark bands (groups 7 and 8) near distal end of arm.
Arm B2:    Puff with distal dark bands (groups 8 and 7) about 1/3 from end of arm, possibly as blaylocki B1
Arm C1:      possibly as C2 of blaylocki
Arm D1:   
Arm D2:    Simple inversion of proximal half of arm.
Arm E1:    1 - 3e, 5 - 10b, 4 - 3f, 10c - 13                                i.e. as maturus, stigmaterus, blaylocki
Arm E2:    approx. 1 - 3e, 6 - 8, 5, 9 - 10b, 4 - 3f, 10c - 13
Arm F1:    1, 9 - 2, 10 - 23                                                    i.e. as blaylocki F1
Arm F2:    1, 9 - 2, 10a-d, 17 - 11, 18 - 23                                (Wülker)

Found: Ontario - Copanspin Farm, Dunrobin, Carleton Co. (45.42°N, 75.87°W); Bear Creek, Carlsbad Springs, Russel Co. (45.37°N, 75.47°W).
            Wisconsin - Arboretum, Madison, Dane Co. (43.08°N, 89.42°W).

            Shallow pools, including in creeks.

This species is very close to C. blaylocki, possibly a subspecies.
Some information on larval morphology and a photograph of the chromosome complement is given in Wülker et al. (2009)

See also  C. bifurcatus,  C. sp. c,  C. sp. j,  C. sp. 2a,  C. sp. 2b,  C. 'butleri",  C. decorus Joh.,  C. sp. 3h,  C. sp. 3i,  C. sp. 3j,  C. sp. 3r,  C. harpi,  C. blaylocki,  C. mozleyi,  C. winnelli.

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Modified: 22 June 2021
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