Kern Primrose Sphinx Moth

Euproserpinus euterpe

Description

The thick-bodied Kern primrose sphinx moth, Euproserpinus euterpe, is one of three species of the genus Euproserpinus. It has white hind wings with dark margins, white underwings, and abruptly hooked antennae. It can be distinguished from the similar phaeton sphinx moth by a marginal band on the hind wing that bows inward rather than running straight along the wing.

Behavior

The flight period of the Kern primrose sphinx moth extends from late February to early April. Adults emerge from pupae in the morning, expand their wings, and fly by midmorning. In the early part of the day, the moth basks on bare patches of soil, dirt roads, or ground squirrel and gopher mounds to warm its flight muscles. Individuals live for one or two weeks.

Mating usually occurs before noon. The female then flies low to the ground and deposits one or two eggs on the underside of the primrose (Camissonia contorta epilobioides), the moth's only larval host plant. The larvae develop in the spring, pupate in the soil, and remain inactive until the following spring when they emerge as adults. Some remain in the pupal stage for several years.

Habitat

The Kern primrose moth is found in Walker Basin, an area 4,851 ft (1,470 m) above sea level surrounded by the Greenhorn and Piute Mountains, which are over 6,600 ft (2,000 m) in elevation. The dominant plants on the sandy alluvial soils are filaree, baby blue-eyes, rabbit brush, gold fields, and brome grass. Juniper, oak, rabbitbrush, sagebrush, and pine dominate the surrounding mountain slopes. Winter rains in the basin end by mid-April, and summers are dry and hot.

From the moth's perspective, the most important plant in the habitat is the evening primrose, which grows in dry, disturbed areas, along sandy washes, or adjacent to fallow fields. The plant germinates in February and March, grows quickly, and by mid-June has set seed and dried out.

Distribution

The Kern primrose sphinx moth is endemic to the Walker Basin in Kern County, California. It is considered the rarest sphinx moth in North America. It was thought extinct until rediscovered in 1974 in a barley field on a privately owned cattle ranch in the Walker Basin. The site remains its only known locality. Field surveys from 1975 to 1979 yielded very low numbers, but in 1979 the population increased dramatically, probably as a result of several years of inactive pupae emerging in response to favorable climatic conditions. In the spring of 1990, the U.S. Fish and Wildlife Service field station in Sacramento, California reported that an adult female moth was observed in eastern Kern County, California. The species had not been observed in the wild for several years. A male may also have been present, but the entomologist was unable to get close enough to make a positive identification.

Threats

Land use practices have posed a major threat to the population. The site was repeatedly plowed, disced, and planted from 1962 until the drought of 1975. Since then, cattle have grazed the site, a use that does not seem harmful to the moth or its larval food plant.

A more serious threat to this sphinx moth is the filaree (Erodium cicutarium ), a plant introduced centuries ago by Spanish explorers. The filaree is widely distributed throughout the area, and egg-laying females often mistake it for the evening primrose. Eggs deposited on filaree hatch, but larvae cannot digest the plant and do not survive. This rare sphinx moth also suffers at the hands of collectors who often take the slower-flying females. Federal law now prohibits taking specimens for sale to collectors.

Conservation and Recovery

Although the habitat site is on privately owned land, a 1983 survey of the Walker Basin found the site to support more potential habitat than previously believed. At least three additional colonies need to be established to prevent extinction. Developing propagation techniques, however, may take several years.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

References

Tuskes, P. M. and J. F. Emmel. 1981. "The Life History and Behavior of Euproserpinus euterpe (Sphingidae)." Journal of the Lepidopterists' Society 35: 27-33.

U.S. Fish and Wildlife Service. 1984. "The Kern Primrose Sphinx Moth Recovery Plan." U.S. Fish and Wildlife Service, Portland.