L. Metalmark Butterfly Profile cont.

Lange's Metalmark Butterfly Profile

Lange's metalmark butterfly has a lifespan of about a year, but very little of that time is spent as an adult, fluttering around the refuge.  Most of the lifespan is spent as an egg, a larva or a pupa.  Each butterfly's life begins as a tiny egg, which is laid in late summer on withering leaves at the base of a buckwheat plant.

The only type of buckwheat acceptable to Lange's metalmark butterfly is a subspecies of naked buckwheat (so named because it has very few leaves along its bare stems).  Female butterflies land on the plant, and lay eggs in the leaf axils or on the leaves themselves.  Without buckwheat plants, the females flutter around - and land on other species of plants - but they do not lay eggs.

The eggs stay on the plant until the rainy season arrives, and then they hatch.  The tiny caterpillars, called larvae, crawl off and spend the winter hibernating in the leaf litter below the barren plants.  When spring comes and new leaves appear on the buckwheat plants, the larvae become active again.  Each evening they leave the leaf litter, crawl up the plants, and eat leaves, stems and flowers.  When daylight comes, they crawl back to their leaf litter hiding places.  Growth is dramatic, and the larvae shed their non-growing skins four times before they reach full size.  A fifth molt during the summer allows each larva to enter a pupal stage that lasts anywhere from six to eighteen days.  During this period, it transforms into an adult butterfly with wings.

As an adult, the butterfly finds a mate, seeks nectar from either the buckwheat or from other flowering plants in the vicinity, and flutters around the buckwheat plants.  Females alight to lay eggs on the leaves, and both males and females bask in the sun on the stems and nearby.  Adult butterflies are at the ends of their lives;males live for up to about nine days, and females die within two weeks.

No one knows how long Lange's metalmark butterfly has existed in the dunes along the San Joaquin River, but the dunes themselves might have been created during the last ice age, or during the last several ice ages.  During those ancient times, wind-blown sand was deposited in extensive, sandy fields along the river and down the western edge of the San Joaquin Valley, in patches as far south as the Tehachapi Mountains.  Sand built up to a thickness of over 100 feet in places, and the San Joaquin River slowly cut through some of the deposits have been found remnants of camels, sloths, horses, bison, and mastodons.

Many desert species of plants and animals have spread north and occupied these sandy places.  Presumably, Lange's metalmark butterfly, over the course of countless generations, established itself in the isolated dunes along the river.

Degradation and loss of habitat due to development, the mining of sand for bricks, and the invasion of non-native plants were the primary contributors for the Lange's metalmark butterfly decline in population.

This excerpt was taken from an article written by John Steiner in the Spring 1993 issue of Tideline, the quarterly newsletter of the San Francisco Bay National Wildlife Refuge Complex.