In the post-median and submedian areas of the ventral surface black spots mark the upper and lower wing.

[5] San Bruno Mountain hosts the largest population of Mission blues, a butterfly commonly found around elevations of 700 feet.

The coastal scrubland and grassland the Mission blue requires is found only in and around the Golden Gate of San Francisco.

Ironically, the same harmful toxins which have led to the eradication of several lupines from rangeland are responsible for the protection of the Mission blue larvae, as predators are deterred by the bitter taste.

[8] Of the threats facing the Mission blue, habitat loss due to human intervention and exotic, invasive species are the two most critical.

Residential and industrial development continually threaten Mission blue habitat, such as the 1997-2001 seismic retrofitting of the Golden Gate Bridge.

Despite costing an additional US$1.2 million to comply with environmental standards, the construction project still claimed about 1,500 m2 of butterfly habitat through "incidental take", an exception provided under California law.

Through a type of habitat conservation popular since a 1983 amendment to the Endangered Species Act, the incidental take is offset by off-site mitigation and restoration.

In this case, the San Francisco Highway and Transportation District in cooperation with the National Park Service funded a $450,000 off-site restoration plan.

The main aspect of this plan was to establish about 8 ha of Mission blue habitat in the area of the bridge project.

Today, a small colony occurs on Twin Peaks; the subspecies has also been found in Fort Baker, which is in Marin County.

[5] The caterpillars, extremely small, feed for a short time and then crawl to the plant base, where they enter a dormant state, known as diapause, until the late winter or the following spring.

The butterfly can be sighted as early as late March in the summit of San Bruno Mountain or the Twin Peaks.

[7] The adult Mission blue lives about a week; during this time, the females lay the eggs on the host plants.

Fish and Wildlife Service (USFWS) has a number of habitat conservation programs in effect which includes lands traditionally inhabited by the Mission blue butterfly.

[7] An example of the type of work being done by governmental and citizen agencies can be found in the Marin Headlands at Golden Gate National Recreation Area.