Comprehensive DescriptionRead full entry
General DescriptionThe Western Spring Azure lacks any trace of orange markings on the underside, and has a white-grey underside with black median and marginal dots. Very similar to the Boreal Spring Azure (C. ladon lucia), but in Alberta these two occur together only in the Castle River - Waterton Lakes region. The underside ground colour of nigrescens is lighter than lucia, and the upperside of males is violet-blue, not pale powder-blue as in lucia. Individuals of both species occasionally occur that have coalescent hindwing spots, resulting in a large blotch rather than a number of dots. The taxonomy of this group of species has been very confusing, and research is still ongoing to define the number of species and the appropriate names for this genus in North America; nigrescens and lucia do not intergrade but remain distinct where they occur together in BC and Alberta (Bird et al. 1995, Guppy & Shepard 2001, Schmidt unpubl. data), evidence that they are separate species rather than geographic forms of the same species.