Xerces Blue

The Xerces blue (Glaucopsyche xerces, Boisduval, 1852) was a small gossamer-winged butterfly of the family Lycaenidae, endemic to a narrow band of coastal sand-dune scrub on the northern San Francisco Peninsula. Its entire known world was a few square kilometers of stabilized dune in what are now the Sunset District and the Lobos Creek and Presidio areas of San Francisco. Males carried a shimmering lilac-blue wash across the upper wings; females were browner and more heavily bordered in black. By most accounts it is the first American butterfly, and one of the first insects of any kind in the United States, known to have been driven to extinction by urban development.

Like many lycaenids, the Xerces blue was bound tightly to a small set of partners. Its caterpillars fed on native legumes of the dune, principally deerweed (Acmispon glaber) and lupines, and the larvae appear to have engaged in a mutualism with native ants, which tended them in exchange for sugary secretions. This web of dependence on a specific plant community, a specific soil, and specific insect partners made the species exquisitely vulnerable to any disturbance of its habitat.

That habitat sat directly in the path of a growing city. Through the 1920s, 1930s, and early 1940s, San Francisco’s western dunes were graded, paved, planted, and built over. The host plants thinned, the dune community fragmented, and introduced Argentine ants are thought to have displaced the native ants on which the larvae depended. The last colonies retreated to the protected ground of the Presidio.

The Xerces blue was last seen there in the early 1940s, with sources citing 1941 or 1943. No living individual has been recorded since. The butterfly survives only as pinned specimens in museum drawers, as the namesake of a major conservation organization, and, since 2021, as a sequenced genome confirming that what was lost was a full and distinct species.

Lord Howe Stick Insect

The Lord Howe Island stick insect (Dryococelus australis, Montrouzier, 1855) is a large, heavy-bodied, glossy-black flightless phasmid endemic to the Lord Howe Island group in the Tasman Sea. Adults reach roughly 12 to 15 centimeters in length and can weigh around 25 grams, with females larger than males. Its bulk and dark, hard-shelled body earned it the local names land lobster and tree lobster. For most of the twentieth century it was believed to be extinct.

The insect’s fate was sealed in 1918, when the supply ship SS Makambo ran aground at Lord Howe Island and black rats (Rattus rattus) came ashore. The rats found the large, slow, flightless phasmids easy prey, and within a few years the species had vanished from the main island. By around 1920 no living stick insects could be found, and Dryococelus australis was regarded as extinct.

Yet rumors persisted. Climbers visiting Ball’s Pyramid, a sheer volcanic sea stack roughly 23 kilometers from Lord Howe Island, had reported a dead specimen and signs that something like the lost insect might survive there. In February 2001 scientists David Priddel and Nicholas Carlile, with ranger Dean Hiscox, climbed the stack and found a tiny relict population, on the order of 24 individuals, living beneath a single Melaleuca shrub.

What followed is the family’s hopeful counterpoint, a genuine Lazarus story. A captive-breeding program begun at Melbourne Zoo in 2003, built from a handful of founders, has since reared thousands of insects. With the eradication of rats and mice from Lord Howe Island completed in 2019, the long-term goal of returning the land lobster to its home island has moved within reach.