‘When the tiny wings of the last Xerces blue butterfly ceased to flutter, our world grew quieter by a whisper and duller by a hue.’ -- veterinarian and author, Mark Jermone Walters
The Xerces blue (Glaucopsyche xerces) is an extinct species of butterfly in the gossamer-winged butterfly family, Lycaenidae. The species lived in coastal sand dunes of the Sunset District of San Francisco Peninsula.
They were a small, brightly colored butterfly characterized by iridescent blue on the upper wing surfaces of males, and pale spots below. The butterflies fed on vegetation belonging to the genus Lotus and Lupinus. The loss of the Lotus plant that the butterfly fed on while in its larval stages is believed to be one reason for the extinction of the Xerces blue. The plant could not survive in the disturbed soils due to human development, and was no longer available to the Xerces blue. Lupin, Xerces blue's other vegetative food source, was not suitable for the larval stages.
The Xerces blue is believed to be the first American butterfly species to become extinct as a result of loss of habitat caused by urban development. The last Xerces blue was seen in 1941 or 1943 on land that is part of Golden Gate National Recreation Area.
The Xerces blue today lives on, lending its name to the Xerces Society, a non-profit organisation that is focused on the conservation of invertebrates and their environments.