Female: Coloration as in males but coloration darker, legs blackish.
Wing length 4.17 mm; VR 0.95-0.96; 28-43 setae on squamal fringe in 2-3 rows; wing coloration darker than in male.Head: Frontal tubercles about 31 µm long; antennal proportions (micron): 195 : 140 : 125 : 117 : 265; AR 0.46; A5/A1 1.36. Palpal proportions (segs 2-5): 70 : 211 : 257 : 351. 39 clypeal setae.
Pupa: Described by J.E. Sublette in Wülker, Sublette & Martin (1991).
Larva a small to medium (male 11.2 mm) plumosus- or thummi-type (may be pH dependent?), with posterior ventral tubules usually slighlty longer (ant. 1.56 mm; post. 1.60 mm) and coiled. Anal tubules relatively long, ventral pair longer (480,540 µm) and 4.8-5.4 times longer than wide. Gular region slightly darkened, frontoclypeus pale.
Mentum with relativley pointed teeth; c1 tooth relatively broad with short parallel sides, c2 teeth moderately well seperated.
Cytology: 4 polytene chromosomes with thummi arm combination AB, CD, EF, G.
Arm G usually closely paired with a Balbiani ring about 1/3 from one end, although specimens from South Dakota had a nucleolus immediately distal to the BR. Nucleolus is near the centromere in arm D.
Polymorphism in arm G near distal end, which homozygous in South Dakota specimens, and instead may be heterozygous for an inversion of about 2/3 of arm G. Polymorphism for arm F also occurs in South Dakota.
Found: Ontario - Point Pelee National Park (41.959, -82.518) (NCBI)
Arkansas - 40 km sw. Little Rock, Saline Co. (Type locality) (plumosus-type)
Illinois - Bradley's Acid Pit (37.90, -89.53), Jackson Co. (thummi-type)
New York - 2-2.5 km e. Middleport (43.22, -78.47), Orleans Co. (plumosus-type)
South Dakota - 3.5 km w., 5 km s. Lake Andes, Charles Mix Co.
Pools with low pH.
Morphology of all life stages, and cytology described by Wülker, Sublette & Martin (1991). Some ecological data given by Harp and Campbell (1973), as C. plumosus; Harp and Hubbard (1972), as C. n.sp. and Bates and Stahl (1985), as C. nr. maturus. The South Dakota population may represent a distinct species, however more samples are required to clarify this. In the meantime it is assumed that this is just geographic differentiation.
The Barcode sequence of the mitochondrial COI gene, from a larvae collected along with the paratypes from Bradley's Acid Pit, is available on the BOLD database (CotW024-08). Further sequences from Pt. Pelee National Park, Ont., Canada are available in NCBI (incl. KJ165251).