The Fenders blue butterfly prefers to eat lupine and other plants that shoot up through the grass. They are said to be very alert to potential predators, dropping from the leaves to the ground at any sign of danger. The butterfly larvae are said to attach themselves to the lupine, feeding on it until emerging as adults in the late spring. The adults get nectar from plants such as wild onion, pink checkermallow and flax. Adults only live about nine and a half days, laying eggs on the lupine. The larvae then go dormant from early summer until the following spring, remaining at the base of the plant in the winter. They each attach to the newly sprouted lupine in the spring.

The mission blue butterfly (Icaricia icarioides missionensis) is only found in the San Francisco Bay area and are commonly found at elevations of around 700 feet. This butterfly has a wingspan ranging from 1 to 1.5 inches. Males usually have a white fringe and a dark black border with silver blue to violet blue upperwings. Females have dull brown upper wings and only small traces of blue. Both sexes’ underwings are silver gray or brownish with black speckles.