3/4-1 1/4" (19-32 mm). Above, male blackish-brown, with occasional blue scaling at wing bases; female lustrous, pale gray-blue, black-bordered, with extensive whitish suffusion. Below, both sexes pale ash-colored to bluish-white, HW irregularly black dotted, with dusky marginal spots large and distinct along entire border.
Spring Azure similar below but much bluer above. Female Eastern Tailed Blue has tails and orange spots.
Egg greenish, ribbed. mature caterpillar uniform whitish blue-green, faintly yellow tiger-striped (not checkered like Spring Azure); feeds on goat's beard (Aruncus dioicus). Chrysalis brown, flecked black; overwinters.
1 brood; April-early May.
Rich, moist, deciduous forests, especially shaded northern slopes where goat's beard grows.
Illinois and W. Pennsylvania south to Missouri and North Carolina.
Only recently distinguished from the widespread Spring Azure, with which it flies, the Dusky Azure is much rarer and more local. These blues imbibe moisture from damp sand and dew and may take nectar at violet and geranium flowers. In most blues the male is blue and the female grayer; the Dusky Azure reverses this pattern.