Many of the more than 14,000 butterfly and moth species in North America are at risk; some have gone extinct. Once abundant in San Francisco, California, the Xerces blue was the first North American butterfly species known to disappear because of human activity—it was last seen in the 1940s.

Much of San Francisco was once covered in sand dunes with low shrubs, wildflowers and lots of insects. But as people built new neighborhoods and the city grew, the sand dunes began to disappear. Without enough lupines and other dune plants to sustain populations of the species’ caterpillars, they could not survive.

Over time, Xerces blues have become a symbol of the danger humans pose to insects—as well as the possibilities for us to help them. Founded in 1971, the Xerces Society for Invertebrate Conservation was named for this lost species. Today, the society conducts a range of scientific, advocacy and outreach programs, monitoring insects including monarch butterflies and bumblebees, and helping conserve 2.5 million acres for pollinators and other insects so far.

Xerces Blue Butterfly
Glaucopsyche xerces
1.1-1.2 inches (27-30 mm)
Ecological Role
Pollinator, Herbivore
AMNH Specimen Number
AMNH_IZC 00329559 and AMNH_IZC 00329560
California, U.S.