Adult:

Male terminalia (left) and superior volsella (centre) and other superior volsella and gonostylus (right) of C. oppositus type specimen.
Superior volsella of this specimen of D-type, between d and e of Strenzke (1959).

Details of the type specimen are given here.

Four forms were recognized by (Martin & Lee 1984), mainly on the basis of larval polytene chromosome banding patterns.    A fifth form, noted by D.H.D. Edward (unpubl.), occurs in Western Australia
No means of reliably distinguishing the adults is known.  However, the type specimen is a large adult and similar large adults were collected near the large central lakes of Tasmania, and these were associated with a single larval type, therefore called form oppositus (o).

The other forms are:
form connori (c)
form tyleri (t) - see C. 'tyleri'.
form whitei (w) - results for this form suggest that it may be a composite of several other more or less differentiated forms - see C. oppositus MD variants.
The forms can be reasonably separated on the basis of allozyme and inversion frequencies.
form 'edwardi' (e) - this should also be recognized as a distinct species.

All these forms are essentially similar in coloration and morphology of hypopygium.  Further study is required to see if characters exist to separate the forms.
There is also a further related species, C. 'tasmaniensis' with only three polytene chromosomes, known from a single larvae

Molecular Data:mtCOI - GenBank (AF110155 - f. connori, KJ946667-KJ946677) and BOLD.  These sequences are shared between the forms of C. oppositus and with C. 'tyleri', presumably due to ongoing hybridization.
mtCyt B - GenBank (AF109698 - f. connori) also KJ946795 & KJ946796
gb2B - Genbank (AJ003799)
CAD1 - GenBank (KJ946479 - KJ946493)
and other genes.

The basic evidence for the recognition of the forms was given in Martin (2011a).

Found: Australian Capital Territory - Acton (-35.30°°S, 149.12°E)(w); 5 Km O’Connor (w), Uriarra (-35.33°S, 148.85°E) (w).
            New South Wales - Barmah Ferry (w); Boggy Swamp Creek, n & e. Putty (w); 13 Km s. Bombala (w); Camden
            Sewage Ponds (-34.05°S, 150.68°E) (c, o, w); Colo (-33.42°S, 150.80°E) (o, w); Station Creek,
            Delegate (-37.05°S, 151.93°E) (w); 30 Km n. Holbrook (abt.-36.0°S, abt 147.08°E) (w); Jeir Creek (-37.08°S, 149.07°E) (w);
            Kiandra (-33.88°S, 150.00°E) (c, o, w); Macquarie Pass (-34.57°S, 150.66oE) (w); 3 Km s. Nowra (-34.90°S, 150.60°E) (w);
            Tarago Swamp (-35.00°S, 149.50°E) (o, w); 13 Km n. Tooma Dam (-37.55°S, 145.87°E) (w or c).
            South Australia - Barmera (-34.25°S, 140.47°E) (o); Lake Leake (37.617°S, 140.583°E) (o) and Lake Edward (37.633°S,
            140.600°E) (o) via Kalangadoo; Mambray Ck, D.C. of Mt Remarkable -32.83°S, 137.98°E) (opp.gp.); Warren Gorge (-32.11°S,
            138.00°E), n. Quorn (w); Wilpens Pound, Flinders Ranges (-31.88°S, 138.42°E) (w). Kangaroo Island: Kingscote (w).
           Tasmania (type locality)(o): - Arthur River (c); Bakers Beach (w); Bellerive (c, o); Bicheno (c); Butler Island, Gordon River (o);
            Cambridge (o); Campbelltown (o); Coles Bay (o); Fossey River (c, w); George Town (c, o); Geeveston (-43.16°S, 146.90°E) (o);
            Ida Bay (c, o, w); Lake Crescent (o); Little Swanport (o); Manning River, Sandy Bay (w); Maydena –(42.67°S, 146.62°E) (c);
            Montana (-41.55°S, 146.58°E); 15 Km Queenstown (c, o); Smithon (-40.83°S, 145.08°E) (c,o,w); Swansea (-42.13°S; 148.09°E) .
            (c, o); Wynyard (c) Flinders Island - Mt. Strezleckie (w): King Island - Porky Lagoon (o); Sea Elephant River (c):
            Victoria - Airies Inlet -38.47°S, 144.10°E) (w); Albert Park (-37.85°S, 145.05°E) (w); Anglesea (-38.38°S, 144.18°E) (c, o, w);
            Armadale (-37.855°S, 145.000°E) (w); Ballarat East (-37.55°S, 143.88°E) (o, w); Balwyn North (o); Beech Forest; Box Hill North
            (-39.82°S, 145.12°E) (w); Bulleen (-37.77°S, 145.09°E) (w); Exhibition Gardens, Carlton (37.78°S, 144.95°E) (w); Cann River
            (-37.57°S, 149.15°E) (o, w); Cumberland River (w); Longlea (w); Eildon (-37.14°S, 145.54°E) (w); Elphinstone (-37.12°S,
            144.33°E) (c, w); Emerald (-37.93°S, 145.43°E) (w); e. Forrest (-38.52°S, 143.73°E); Frankston (-38.08°S, 148.08°E) (w);
            Harcourt (-37.02°S, 144.25°E); nr. Hepburn Springs (-37.26°S, 144.11°E) (c, w); Horden Vale (w); Kew North (-37.786oS,
            145.043oE); between Linto & Skipton (-37.68oS, 143.46oE) (w); Little River (-37.93°S, 144.50°E); Lodge Rd.,
            Grampians (-37.12°S, 142.30°E) (o, w); Longlea (-36.75°S, 144.33°E) (w); Davis Creek, Mallacoota (-37.57°S, 149.75°E) (o, w);
            Manns Beach (o); Maryborough (w); Botanic Gardens, Melbourne (-37.83°S, 144.97°E) (w); Melbourne University (-37.796°S,
            144.960°E) (w); Mitcham (-37.818°S, 145.197°E) (o); Moggs Creek, Angehook Forest Park, (-38.45°S, 144.05°E) (c, o, w);
            Mount Macedon -37.42°S, 144.58°E) (c); Narbethong (-37.57°S, 145.65°E) (w); Orbost (-37.50°S, 148.33°E) (o);
            w. Orbost (-37.50°S, 148.33°E) (o, w); Parker Road, Cape Horn (w); Panton Hills (-37.63°S, 145.23°E) (w); Preston West
            (-37.74°S, 144.50°E) (w); Reedy Creek (c, o); nr. Sale (o); Sassafras (-38.58°S, 147.67°E) (w); Spout Creek, nr. Lorne (-38.461°S,
            144.01°E) (w); Templestowe (-37.77°S, 145.11°E) (o, w); Upper Clear Spot; Vermont (-37.83°S, 145.20°E) (c w);
            Wangaratta (-36.19°S 146.18°E); Warburton (-37.75°S, 145.70°E); Warrandyte (-37.77°S, 145.20°E) (c, o, w); West Preston (w);
            Squeaky Beach & Tidal River, Wilson's Promontory (-39.02°S, 146,32°E) (w), Wilsons Promontory (-39.05°S; 146.32°E) (o, w);
            Lake Elusive nr. Wingan Inlet (-37.73°S, 149.45°E); You Yangs reserve (-38.00°S, 144.46°E) (w).
            Western Australia - Lake Gwellup (-31.867°S, 115.800°E) (e).