Presumed Extinct: On a Wing and a Prayer

LOST SPECIES OF THE BAY AREA

Presumed Extinct: Strohbeen’s Parnassian butterfly, lotis blue butterfly

As with the presumed extinct ivory-billed woodpecker reported in Arkansas in 2004, there is always the chance that a long-lost plant or animal will be rediscovered, thanks to persistent searching and luck. That’s true even in a busy metropolitan area like the San Francisco Bay Area. In May 2005, botanist Michael Park stumbled upon a population of Mount Diablo buckwheat (Eriogonum truncatum) on the slopes of Mount Diablo. The buckwheat was a species long thought extinct, last seen in 1936 by UC Berkeley botany graduate student (and later Save Mount Diablo cofounder) Mary Bowerman. 

Spurred by the rediscovery of the buckwheat, it bears asking today which plants and animals endemic to – but presumed extinct in – the San Francisco Bay Area scientists continue to search for in the hope they may still be hanging on by a thread, waiting to be found and protected.

Strohbeen’s Parnassian butterfly (Parnassius clodius strohbeeni)

lotis blue butterfly (Lycaeides idas lotis)

In the days before Lombard Street and the Golden Gate Bridge, the endemic Xerces blue butterfly (Glaucopsyche xerces) called the San Francisco Peninsula its home. Only 23 years after its description in 1852, lepidopterist Herman Behr noted its incipient extinction as the city overtook the sand dunes. At the Presidio’s Lobos Creek in 1941, future UC Davis entomology professor W. Harry Lange unknowingly netted what would turn out to be the last recorded Xerces and popped it in a killing jar. Revisiting the Presidio a few years before his death, Lange lamented: “I always thought there would be more. I was wrong.”

Two more local butterflies followed the Xerces into oblivion. The Sthenele satyr (Cercyonis sthenele sthenele) and Pheres blue (Plebejus icariodes pheres) were collected by Forty Niner-turned-entomologist Pierre Joseph Michel Lorquin around 1850 in the city’s westerly dunes. By 1880, the Sthenele satyr had disappeared. About the Pheres blue we know only that it was reported at 14th Avenue and Taraval Street, and on the dunes west of 20th Avenue. The first population was extirpated around 1926, the second by 1940. By 1950, the Pheres blue had vanished.

Strohbeen's Parnassian butterfly (Parnassius clodius strohbeeni). Illustration by Devin Cecil-Wishing.

In the wake of San Francisco’s doomed dune butterflies — the Xerces, Pheres, and Sthenele — two additional butterflies may have fluttered their last flight within living memory. In the Santa Cruz Mountains, Strohbeen’s Parnassian butterfly (Parnassius clodius strohbeeni) glided through the redwoods, frequenting well-lit canyon bottoms and stream zones, unique in itself since other species of Parnassian inhabit higher elevations. Strohbeen’s Parnassian was first collected in 1923 by John Strohbeen during a fishing trip in the Santa Cruz Mountains at a site later destroyed by road construction. The butterfly’s larval host plant, western bleeding heart (Dicentra formosa), later waned in numbers due to over-collection for the nursery trade. In 1956, entomologist James Wilson Tilden observed the last known living members of this species — a small colony in the vicinity of Bonny Doon atop Mount Ben Lomond.

Lotis blue butterfly (Lycaeides idas lotis). Illustration by Devin Cecil-Wishing

A more likely candidate for survival is the federally endangered lotis blue butterfly (Lycaeides idas lotis). The lotis blue was described in 1879 by entomologist Joseph Albert Lintner based on a specimen labeled “Mendocino” from the collection of renowned lepidopterist William Henry Edwards. Who wielded the net remains a mystery, one that vexed even novelist and amateur lepidopterist Vladimir Nabokov when he revised the taxonomy of North American blues in the 1940s. The lotis blue frequented Mendocino and Sonoma counties’ wet meadows and sphagnum-willow bogs. It’s not known what drove the species toward extinction, but urban development, fire suppression, drought, and groundwater drawdown are all likely suspects. Today, suitable habitat for the species is restricted to a single bog on PG&E land in Mendocino’s Pygmy Forest south of Fort Bragg. The lotis blue was last seen there in 1983, and its suspected host plant, seaside bird’s-foot trefoil (Lotus formosis-simus) — though otherwise common — hasn’t been seen there since 2000.

Over the years, entomologist Richard Arnold has kept an eye out for sun-dappled forest clearings or boggy spots that might harbor long-lost butterflies. “You always hope that maybe there’s some place you haven’t been yet,” he says. “The problem is, you run into small stands of food plant, but not the large stands needed to sustain a population.” With so many people tuned in to butterflies, “it’s unlikely a butterfly could go unnoticed for years on end,” says retired UC Berkeley entomologist Jerry Powell. But it happens. In 1990, Arnold was part of a team that happened on the only known population of federally endangered Behren’s silverspot butterfly (Speyeria zerene behrensii) near Point Arena, a species that hadn’t been seen in many years.

Field Guide to the Lost Species of the Bay Area

SPECIES: Strohbeen’s Parnassian butterfly (Parnassius clodius strohbeeni)

LISTING STATUS: none

FIRST/LAST RECORDED: 1923/~1956

RANGE: known only from the Santa Cruz Mountains in Santa Cruz County

HABITAT: host plant is western bleeding heart (Dicentra formosa); redwood forests, well-lit canyon bottoms, stream zones

FIELD NOTES: of the Parnassian butterflies (P. clodius), Strohbeen’s Parnassian is a lighter sub-species restricted to the Santa Cruz Mountains; its closest cousins are found in the high inner North Coast Range, the Klamath Mountains, and the west slope of the Sierra Nevada; the Strohbeen’s Parnassian’s flight period is late May to early July

RESOURCES:

Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, by Arthur M. Shapiro and Timothy D. Manolis

_______________________________________________

SPECIES: lotis blue butterfly (Lycaeides idas lotis)

LISTING STATUS: federally endangered

FIRST/LAST RECORDED: 1879/1983

RANGE: scattered locations throughout Mendocino and Sonoma County; last known from a single location on PG&E land in Mendocino County’s Pygmy Forest

HABITAT: suspected host plant is seaside bird’s-foot trefoil (Lotus formosissimus); wet meadows, spagnum-willow bogs

FIELD NOTES: the lotis blue is often described as a larger version of its fellow blue, the Melissa blue butterfly (Lycaeides melissa); the lotis blue’s flight period is mid-April to June

RESOURCES:

Field Guide to Butterflies of the San Francisco Bay and Sacramento Valley Regions, by Arthur M. Shapiro and Timothy D. Manolis

Lotis Blue Draft Recovery Plan, March 13, 1996, by the U.S. Fish and Wildlife Service

The account excerpted above was originally featured in the October/December 2007 issue of Bay Nature magazine.

Illustrations by Devin Cecil-Wishing.

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