AdultE. icelus is easily distinguished from other Erynnis in BC by the lack of a submarginal group of clear white spots on the forewing. The male valve has a short ventral process and a small, rounded middle lobe. Although the wings are variable in pattern, there is no clear way to distinguish the sexes except that the male has a costal fold. The length of the forewing is 1-4-1.6 cm.
Immature StagesScudder (1889b) described the life cycle. The egg is very pale green. The larval head is uniform light red brown; the ocelli are red brown on a black stripe. The first thoracic segment is yellow and the rest of the body is grey-green, caused by fine whitish granulations on a pale green surface. The larva is marked by a dark median stripe and a pale lateral stripe.
SubspeciesNone. The type locality of the species is New England.