Two broods of KB usually are produced each year. Eggs that have overwintered from the previous year hatch in April. The larvae feed on wild lupine leaves and mature rapidly. The larvae pupate in May, with adult butterflies emerging very late in the month in most years. The adults typically are in flight for the first 10 to 15 days in June, when the wild lupine is in bloom.
Females lay eggs on or near the wild lupine plants.
The eggs hatch in about one week, and the larvae feed for about three weeks before they pupate. Adults of the second brood usually appear in the second or third week of July. This time, females lay eggs among plant litter, on grass blades at the base of the lupines, or on lupine pods or stems. By early August, no adults remain. The eggs do not hatch until the following spring.