Butterflies are some of the most fascinating animals. All go through several very distinct life stages. Butterfly eggs are deposited near edible plants and when they hatch, a larva emerges. Butterfly larvae are commonly called caterpillars. Many caterpillars in the Bay Area taste terribly to keep predators away. Their bright coloration informs predators of this inedibility. A caterpillar eats solid plant foods until it has grown to its maximum size. Then, it finds a safe place and spins a cocoon, or chrysalis, around itself. During this stage of metamorphosis, many incredible changes occur in addition to wing growth. The pupa, as the butterfly at this stage is called, loses its first sets of legs and eyes and grows different sets useful for flying. It loses its ability to eat solid foods, and grows a proboscis, a coiled tube used to collect nectar. After a period as short as two weeks or as long as a year, the butterfly emerges. Adult butterflies live in swarms, noticeable when they hilltop, in which males congregate on hills, and females seek them to mate with, and when they migrate, a behavior in which they fly to warmer climates. Thanks to the very temperate climate and diverse ecosystems of Northern California, many fascinating butterflies summer here and many more remain year-round. Four species in particular are a common sight in the Baylands: the Western Pygmy Blue, the Anise Swallowtail, the West Coast Lady, and the Cabbage White.
|The Western Pygmy Blue is the smallest butterfly in California, no more than three-quarters of an inch long, or about the size of a nickel. Its eggs are pale-green and turban shaped, while the caterpillars that emerge from them are green with white and yellow lines. These caterpillars have an interesting gland, which secretes a fluid very appetizing to ants. Hence, the ants are satisfied and do not attempt to eat the caterpillar itself. A Pygmy's chrysalis is yellowish-brown with brown dots, and hairy. Seen from above, adult male Pygmies are blue, while females are brown with blue bands at the bases of their wings. Both have similar patterns on their undersides, pale brown with wavy white lines and iridescent spots on the outer edge of the hind wing. Adults have a novel way of cooling themselves, by drinking water and spurting it through their digestive system, a behavior called pumping. Pygmies migrate into the San Francisco Bay Area in March and stay as late as October.|
|The Anise Swallowtail is the smallest yellow swallowtail. It has round, smooth, pale green eggs. Its caterpillars are black with orange spots when young, but turn green with black bands as they get older. They have odor-producing organs called osmalia just behind their heads, which stick out when they are disturbed and serve to protect them. This swallowtail's chrysalis is either green or brown. Adult are deep yellow with wide black bands, and have the long, tail-like wing projections common to all swallowtails. These butterflies used to feed on wild parsley plants, and hence were known as Western Parsley Swallowtails, but the destruction of the native vegetation in the area has forced these butterflies to feed on anise, and even carrot tops. Like the Pygmies, they migrate into the area in March and stay through October.|
|The West Coast Lady gets its name from being the only butterfly of its kind that lives in the western portion of the United States alone. The Lady lays green, barrel-shaped, ribbed eggs. Caterpillars vary in color from tan through brown to black with yellow lines, but all are spiny, and wrap leaves around themselves, as shelter. The Lady's chrysalis is rough, knobby, and brown with golden specks. Adults are orange and black, and can be identified by an orange bar on the upper wings and very large eye-spots on the underside of the hind wings, which are used to fool predators. Ladies can be found in the Bay area all year long, and have several broods a year, thanks to the temperate winters.|
|The Cabbage White, initially introduced to North America from Europe, has spread throughout the United States. The White has pale-green, pear-shaped eggs, which hatch into bright-green, velvety caterpillars with tiny black specks, and dark and yellow lines. The favorite foods of the caterpillars are cabbage, cauliflower, and other plants of the mustard family, and hence, they are widely viewed as pests and have earned the name of Imported Cabbage Worm. The chrysalis is either bright green or pale brown. Adults are a dull-white color with dark tips on their forewings, and reproduce all year round.|
As more of the Bay Area comes under human control, and more marshlands are filled in for human occupation, the plants on which these butterflies feed become increasingly uncommon, and butterflies find themselves with nothing to eat. While these four butterflies are not endangered, others in the Bay Area are, and all their numbers have declined in the past years. As butterflies disappear, so too will all the birds that feed on them. The diverse habitats of California are some of the most beautiful in the world, and it is important for all of us to work to preserve them.
Garth, John S. and J.W. Tilden. California Butterflies. Berkeley, CA: University of California Press, 1986.
"Butterflies of California." Butterflies of North America. <http://www.npwrc.usgs.gov/resource/distr/lepid/bflyusa/ca/toc.htm> (4 June 1998).
Tilden, J.W. Butterflies of the San Francisco Bay Region. Berkeley, CA: University of California Press, 1965.
United States Butterflies: http://www.npwrc.usgs.gov/resource/distr/lepid/bflyusa/bflyusa.htm
Electronic Resources on Lepidoptera: http://www.chebucto.ns.ca/Environment/NHR/lepidoptera.html
The Lepidopterists' Society: http://www.furman.edu/~snyder/snyder/lep/
North American Butterfly Association: http://www.naba.org/
The Butterfly Website: http://www.butterflywebsite.com/
Butterfly Newsgroup: sci.bio.entomology.lepidoptera