In 1977, the Karner blue became the first insect to be listed on the New York State Endangered Species List . A member of the pea family, it is the only known food source of the larvae of the Karner blue butterfly. Without this plant, the butterfly cannot exist.
Wild lupine does best in sandy soils, in areas that are occasionally razed by wildfires.
Karner blues rely on lupine for their whole life cycle. In April, tiny butterfly eggs hatch after spending the winter attached to the lupine stems. The newly born caterpillars feed avidly on the lupine's newly sprouted spring leaves. The caterpillars pupate in May and emerge as adults at the end of the month. In June, these first-brood females lay their eggs, again on the lupine stems, and a second brood of larvae hatch about a week later.