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KERN PRIMROSE
SPHINX MOTH
Euproserpinus euterpe
One of three species of sphinx
moths, the Kern primrose sphinx moth occurs on the Carrizo Plain
National Monument in San Luis Obispo County, in the Cuyama
Valley of Santa Barbara and Ventura counties, and the Walker
Basin of Kern County. It was originally thought to only occur in
Kern County (hence the name), but new populations were recently
discovered in Santa Barbara and Ventura counties. Two
populations are now known to exist on the Los Padres National
Forest, near Ventucopa in the Cuyama Valley.
The Kern primrose sphinx moth is a day-flying, moderate sized
moth with a wingspan of 1-3 inches. Its hindwings have a
distinct white band, and the top surface of its antenna have
white scaling. The colorful larvae are hairless, but they do
have a horn or spur. Interestingly, pupae are known to delay
metamorphosis into adult form and stay underground for multiple
years during drought periods. The moth larvae require a specific
host plant for early nutritional needs, certain primrose and sun
cup species, and it was believed they would starve and die if
their eggs were laid on a non-host plant. However, new research
has found that the larva are actually capable of short forays in
search of their host plants.
The moth is usually found along
sandy washes, in which the sand has the proper compaction and
moisture content for burrowing larvae. The washes at the Carrizo
Plain where the Kern primrose sphinx moth was observed flow
north from the Caliente Range and along the Elkhorn Scarp,
whereas the washes in the Cuyama Valley with confirmed sightings
flow west from the Los Padres National Forest into the Cuyama
River by Ventucopa and north into the Cuyama River near the town
of New Cuyama.
Threats
The Kern primrose sphinx moth was listed as threatened under the
federal Endangered Species Act in April 1980. In fact, the
species was believed to be extinct until it was rediscovered in
1974, when a surviving population was found in Kern County.
Sphinx moths are valuable to insect collectors, who have
historically posed a threat to these small populations. Female
Kern primrose sphinx moths fly slower and are easier to capture,
which may have led to a serious depletion in females at Walker
Basin.
Today a more serious and common threat is habitat destruction
and degradation. The moth’s specific host plant requirements
make the species particularly vulnerable to habitat degradation
that results in the loss of their primary food plant, the sun
cup or evening primrose Camissonia contorta. Such habitat
degradation can be caused by cattle and sheep grazing,
pesticides and herbicides, off-road vehicle trespass, road
maintenance, and development, as well as the expansion of the
non-native, invasive, low-growing weedy plant, filaree. Filaree
is an excellent nectar source for adult moths, and adult females
will often lay their eggs on this plant. However, the larva
cannot eat the plant and die unless they are able to relocate to
their appropriate host plant nearby.
In addition, in 2005 the U.S.
Forest Service approved a plan to expand oil drilling on 52,075
acres of the Los Padres National Forest. One of these drilling
areas is in Kern primrose sphinx moth habitat in the Cuyama
badlands.
Conservation Efforts
The areas that offer some protection for the moth include the
two populations at the Carrizo Plain on Bureau of Land
Management land and two populations at the Cuyama Valley on U.S.
Forest Service land. This would constitute about one-third of
the entire known Kern primrose sphinx moth population. The
populations on public lands are afforded some protection,
including fencing installed around known populations and
monitoring and population surveys when the flight season for the
moth starts. All the involved federal agencies (U.S. Fish and
Wildlife Service, U.S. Forest Service, and the Bureau of Land
Management) also meet annually to coordinate efforts to protect
the moth. However, the adequacy of these measures are unknown,
and many of these populations remain vulnerable to habitat
destruction.
As a federally-protected species, the Kern primrose sphinx moth
is also protected by the Lacey Act, making it unlawful to
import, export, sell or receive, or transport any moths whether
alive or dead, including parts, products, eggs, or offspring.
In 1984, the U.S. Fish and Wildlife Service approved a recovery
plan for the species, but a new recovery plan needs to be
completed to incorporate important new findings including the
expanded population distribution (beyond Kern County in the
Carrizo Plain and Cuyama Valley) and the capability of larvae to
traverse small distances to find proper host plants. ForestWatch
will continue to monitor each federal agency’s work surrounding
the protection of the Kern primrose sphinx moth, and will work
to see that this rare moth continues to call central California
home.
ForestWatch will also continue
its efforts to protect any Kern primrose sphinx moth habitat
from oil drilling.
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