Lange's Metalmark Butterfly

Apodemia mormo langei

Description

Lange's metalmark butterfly, Apodemia mormo langei, is a bright reddish-orange butterfly, brightly patterned above with four black-bordered, pearl-white squares on the front wings. Back wings have large white squares and polygons. The wingspan is 0.8-1.25 in (2-3 cm).

Behavior

The swift-flying Lange's metalmark butterfly produces one brood in a season. Adults emerge in early August and can be observed until mid-or late September. Numbers peak two or three weeks after the earliest date of eclosion, the emergence of the butterfly from the pupal case. The peak in male emergence is generally earlier than that of females.

Egg laying occurs throughout the adult flight period. The gray eggs are laid on the lower half of the larval food plant, a subspecies of naked buckwheat,Eriogonum nudum var. auriculatum. Eggs are placed on the stem axils on the less pubescent surface of the withered foliage. They often are deposited in clusters of two or four but may infrequently be laid singly. The eggs remain attached and dormant until the rainy season, at which time the larvae hatch and crawl to the base of the plant where they over-winter and feed if new foliage is available. The larvae are nocturnal feeders and they begin to feed on new plant growth in late fall or early winter. Pupation occurs in mid-summer in the litter at the base of the buckwheat.

Adults of both sexes are perchers and are capable of long movements between observed perches. The majority of males move less than 100 ft (30 m) while females may travel up to 1,200 ft (360 m). Both sexes prefer buckwheat flowers as perches and as a nectar source. Female butterflies visit a greater variety of secondary nectar sources than do males, which tend to perch or aggregate more than females. The greater vagility of the females is thought to result from their search for suitable egg-laying sites and secondary nectar sources. Usually neither sex, however, moves very far from the buckwheat plants. Nevertheless, females tend to move more frequently between clumps while the less-mobile males remain within a single clump of buckwheat for various periods of time.

It was previously thought that adult females lived nine days or less while males presumably were even shorter lived. Both sexes, however, live approximately one week.

Habitat

This butterfly inhabits stabilized sand dunes along the San Joaquin River. Its primary host plant is a subspecies of naked buckwheat (Eriogonum nudum var. auriculatum ). It depends on host plants for breeding but feeds on the nectar of other wild-flowers, if buckwheat is not available.

Distribution

Lange's metalmark is endemic to the Antioch Dunes, which are situated at the confluence of the San Joaquin and Sacramento rivers east of the City of Antioch in Contra Costa County, California. By the late twentieth century, the range of this sub-species had been reduced to about 15 acres (6 hectares). Annual surveys during peak breeding season produced counts of 150 butterflies in 1986, 140 in 1987, and 500 in 1988. The total population is extrapolated from these counts and is thought to average about 400.

The U. S. Fish and Wildlife Service (FWS) acquired approximately 70 acres (28 hectares) of the Antioch Dunes, including a portion of the Lange's metalmark's range, adding it as a satellite to the San Francisco Bay National Wildlife Refuge complex.

Threats

The primary factors limiting the size of the butterfly populations are the availability of nectar sources for adults, adequate host plants for egg laying, and sufficient food for larvae. Losses of these habitat components because of human activity in the area have severely reduced population levels. (The buckwheat also serves as a primary nectar and pollen source for many of the sand-nesting bees and wasps present on the dunes.) Invasion by exotic plant species evidently has reduced the potential for reestablishment of such native plants as the buckwheat. Unless the exotic plants are eliminated or reduced to some degree, they will continue to limit the reestablishment of native vegetation. Moreover, additional losses of buckwheat caused by discing for fuelbreaks probably will result in further reductions in the numbers of butterflies. Although most disced and mined areas may eventually support Eriogonum, these areas recover slowly. Possibly other natural mortality factors exist that are not known or understood.

A devastating wildfire in 1976 near the Pacific Gas & Electric east tower destroyed most of the butterfly larvae present and much of the buckwheat stand. By the 1990s, the Eriogonum had largely regained its former numbers, although the size and shrubbiness of the plants apparently was still not yet sufficient to support a self-sustaining colony. Butterflies have been observed at the site of the wildfire since 1977, but these appear to be immigrants.

In the 1980s Antioch Dunes began to feel the negative effects of increased recreational use. Visitors severely trampled and littered the fragile dunes habitat. The coup de grace was applied by the unexpected visit of "Humphrey the Humpback Whale." When this whale—ironically an endangered species, itself—was stranded for a time in the Sacramento River, the highly publicized rescue attempt brought large crowds to the refuge, causing severe damage to plant life. As a result, the FWS closed the Antioch Dunes National Wildlife Refuge to unescorted groups in 1988 and 1989.

Conservation and Recovery

Captive breeding of this butterfly and cultivation of its host plant—along with the removal of introduced plants—may be necessary for its recovery. FWS personnel have discussed importing sand to restore the dunes area. A local utility operating a right-of-way adjacent to the refuge funded buckwheat planting and habitat restoration both on its land and within the refuge.

A public awareness program to provide informational brochures and place interpretive signs has been implemented to alert visitors to the fragility of the dunes habitat.

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

Arnold, R. A. 1983. "Ecological Studies on Six Endangered Butterflies (Lepidoptera: Lycaenidae): Island Biogeography, Patch Dynamics, and the Design of Habitat Preserves." University of California Publications in Entomology 99: 1-161.

Arnold, R. A. 1978. "Survey and Status of Six Endangered California Butterflies." Report. California Department of Fish and Game, Sacramento.