Karner Blue Butterfly Life History: The Karner blue butterfly produces two broods of young each year, a spring brood and a summer brood. Larvae emerge in April from eggs that have overwintered and feed on wild lupine, Lupinus perennis, the only known larval food plant of the butterfly. The larvae are often attended by ants, which collect a sugary solution secreted by the larvae, and in turn may protect the larvae from predation and /or parasitism. Near the end of May, the larvae pupate and adults emerge in late May or early June. The butterfly then mates and lays eggs on the lupine plant. The second brood of butterflies emerge mid-July to early August. Their eggs over-winter to hatch again in April.