Our species profile for this issue is the Large Marble, Euchloe ausonides. The Large Marble belongs to the family Pieridae, which includes the Whites and Sulphurs, a worldwide group of butterflies that often have white or yellow wings.

The Large Marble is restricted to North America, where it is found from Alaska to Manitoba, and south to Nebraska, New Mexico and California. The species occupies most of the western “lower 48” in the USA, also western Canada and the central part of Alaska. In Washington, the Large Marble is found throughout the state east of the Cascades. In western Washington it has been reported only from eastern Whatcom County near the Cascade crest, and recently also from San Juan County.

Adult Large Marbles begin flying as early as late March. In the early spring it flies in low elevation sagebrush steppe, and later in the season in meadows and open forests at higher elevations, ranging upward to treeline where adults have been reported into late June. Llke many early-flying butterflies, the Large Marble spends the winter in its chrysalis stage, ready to emerge in the first warm days of spring.

After mating, the female ausonides lays her eggs, one per plant, on a bud of a mustard plant, frequently one of the delicate purple-flowering Arabis species. The eggs are yellow (becoming orange), spindle­ shaped, attached at one pointed end, and sculptured with longitudinal grooves & ridges. The Arabis host plants are often relatively sparse where ausonides flies, making it possible for a keen observer to find an egg before it hatches. On hatching, the larva feeds on the newly opened flowers, and later the saliques (seed pods), of the mustard. First instar larvae are very difficult to find in the field, but after growing larger the attractive yellow and gray striped caterpillar can be spotted, partly by the feeding damage to the host plant At pupation the elongated light tan chrysalis is usually mounted on some permanent structure, rather than the delicate host plant, as the species is single-brooded and the chrysalis must endure the entire winter.

Large Marble-Egg lnstar

Large Marble-Fifth

Large Marble—Chrysalis                                                              

Large Marble-Adult

Ventrally the adult Large Marble has a beautiful complex pattern of irregular marbling of green bands on a cream background, with interlaced thin yellow wing veins. In this region only the Sara Orangetip (Anthocharis sara) and the Desert Marble (Euchloe lotta) have similar patterns, and the Sara is easily separated by its orange wingtips.

The Large Marble can be distinguished from the Desert Marble, by:

1. The Large Marble is the larger of the two species.
2. Dorsally, there is a black “cell bar” on the forewing near the leading edge, half way between the body and the wing tip. On the Large Marble, this cell bar is narrow and bent; on the Desert Marble it is more square and blocky. Also, on the Large Marble the cell bar is sprinkled with white scales giving it a frosted appearance especially at the front, while the Desert Marble is not so marked.
3. Ventrally, the whitish ground color is flat on the Large Marble, but has a pearly luster on the Desert Marble.
4. Ventrally, on the Large Marble, the green marbling is ve1y irregular and fragmented; while on the Desert Marble it is blockier, even having some straight edges.
5. Ventrally, on the Large Marble, the yellow wing veins are distinct across both the white background and the green marbling. But on the Desert Marble the yellow veins become obscured where they cross the white background areas.
6. The Desert Marble is restricted to lower elevation, sagebrush areas, while the Large Marble can be found much higher and later in the season.

Both of our Marbles will be flying in the first days of early spring, and we eagerly look forward to seeing these early harbingers of another fine butterfly summer.

G’num2001Vol2No1