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Adults of this small tailed butterfly have a 25 to 32 mm wingspan. It is easily distinguished from other butterflies in Alberta because the dorsal wing surface is steel blue with wide dark margins. Ventral wing surface is reddish brown and has a row of black submarginal spots. There is a white postmedian band with a black edge on the ventral hindwing that forms a "W" near tails (Layberry et al., 1998). The surface of eggs lacks spicules (Guppy & Shepard, 2001). Larvae have an olive stripe down the back with red, white, and yellow stripes on each well-defined ridge (Opler & Wright, 1999). Pupae are dark brown (Guppy & Shepard, 2001).

Pupae overwinter in the mistletoe mass (Bird et al., 1995; Guppy & Shepard, 2001). Males perch in tall trees to find receptive females (Opler et al., 1995). Eggs are laid singly on mistletoe and caterpillars eat all external parts of their host plant. Adults only come down from the tops of trees for nectar (Opler et al., 1995). There are larval and pupal parasitoids (Remington, 1958; Shields, 1965) and avian predators of C. spinetorum (Shields, 1965).

In Alberta, this species is dependent on dwarf mistletoe (Arceuthobium sp.) that grow parasitically on pine (Pinus sp.) (Bird et al., 1995). In British Columbia and the United States, they also feed on mistletoe that parasitize fir (Abies sp.), Douglas Fir (Pseudotsuga menziesii), and Larch (Larix occidentalis) (Remington, 1958; Shields, 1965; Guppy & Shepard, 2001). Adults visit flowers for nectar (Shields, 1965; Bird et al., 1995; Layberry et al., 1998).