Lange's metalmark is a fragile, brightly colored butterfly in the Riodinidae family. Adult wingspan varies from to. Dorsal wings are largely black with white spots. Red-orange coloration extends through the inner forward half of the forewing, the hindwing bases, and a small central patch subtended by black. Below, the wings have a more muted pattern of gray, white, black, and orange.
Status and distribution
The butterfly has been classified in the United States as a federal endangered species. Lange's metalmark butterfly was historically restricted to sand dunes along the southern bank of the Sacramento River, and is currently found only at Antioch Sand Dunes in Contra Costa County, California. Most of the habitat is now part of the Antioch Dunes National Wildlife Refuge, administered by the Don Edwards San Francisco Bay National Wildlife Refuge Complex. Recent population counts have ranged from several hundred to more than a thousand individuals. While the Antioch Dunes Recovery Plan of April 25, 1984, has been put under action, no critical habitat has been designated as yet. In the early 1900s, the isolated dune habitat in the Sacramento-San Joaquin River Delta began to experience a dramatic change as human development expanded. The easily accessible sand was harvested to make bricks. Large-scale sand mining and industrial development fragmented the sand dune habitat until only a small portion of the original ecosystem remained. Nonnative grasses and other vegetation encroached on the sand dunes to crowd the few remaining endangered plants. By the time the Antioch Dunes Refuge was established, only a few acres of remnant dune habitat supported the last natural populations of Antioch Dunes evening primrose, Contra Costa wallflower and Lange's metalmark. A reservoir of moving sand is essential to maintain the dynamic ecology of the dunes, as moving sand opens areas for the establishment of seedling plants. Roto-tilling has contributed to the invasion of exotic vegetation that stabilizes the remaining sand-dune habitat and competes with native dune vegetation. Habitat improvement activities have included dune restoration, hand clearing of nonnative plant species, planting buckwheat seedlings and restriction of public access to avoid trampling and fire. A nonprofit environmental group has been breeding the butterflies in captivity since 2007 and periodically releasing larvae and adults back to the wild as insurance against collapse of the remaining wild population.
Life history
All the life stages of Lange's metalmark butterflies are found close to the larval food plant, buckwheat. The eggs are deposited on buckwheat leaves near the leaf petiole during a short mating flight of 10 days' duration. Larvae hatch during the rainy months. Larvae are known to feed only on buckwheat. The adults may use buckwheat, butterweed for nectar. Lange's metalmark butterfly also uses silver lupine for mating. Unlike the many butterfly species that have several generations a year, Lange's metalmark has only one. The fecundity of wild individuals is low. Detailed life history and physiological requirements of this subspecies are unknown.
