Euphydryas editha

Euphydryas editha can be found in scattered, semi-isolated populations in the western United States. Coastal populations range from southern California to western Washington. The species can also be found in locations of the San Bernardino Mountains, Sierra Nevada, higher Cascade Mountains of Oregon to Washington, and in areas of the Great Basin, including central Oregon and the Rocky Mountains. (Radtkey and Singer, April 1995; Scott, 1986)

Edith's checkerspot prefer grasslands and rocky outcrops found in the mountains. They are usually found in areas of nutrient-poor, serpentinitic soils which sustain the native grasslands that they prefer. (Baughman, August 1991; Scott, 1986; Thomas, Singer, and Boughton, December 1996; Weiss, 1999)

Euphydryas editha butterflies are usually orange with checkerboard markings; however, their appearance varies based on the area that they inhabit. Coastal populations are black with red and cream spots; mountain populations are red or mottled with red, black, and cream spots. The higher-altitude populations are smaller and darker in color. The larvae of the butterfly are black, spotted with white or orange, or striped with white. The pupae are white or gray, with black blotches and streaks. (Cohen and August 31, 1996; Scott, 1986)

Euphydryas editha eggs hatch about two weeks after they are laid. Larvae live and feed together in loose silk webs, complete three instars, and enter diapause during the spring. Edith's checkerspot larvae have thick and hairy skins to better withstand summer drying during diapause, and can usually be found under stones as they hibernate. The larvae emerge from diapause the following spring, complete development, and pupate. (Osborne and Redak, January 2000; Scott, 1986; Thomas, Singer, and Boughton, December 1996)

Adult Edith's Checkerspot live about ten days, on average.

(Baughman 1991)

Euphydryas editha are very sedentary - individuals do not move more than 600 meters, or 2000 feet, in their entire lifespan. Perhaps because of this, there are many phenotypically well-defined groups that rise from preferences for different combinations of host plants existing in close proximity of one another. Very little gene flow occurs between these populations. Adults make one flight during March to April on the California coast, June in the Great Basin, and late June to early August above the timberline. (Britten et al., 1995; Sbordoni and Forestiero, 1998; Scott, 1986)

Checkerspots are known to communicate at least on the chemical level. Virgin females release a pheromone which attracts males, allowing them to be located in order to mate. Unseen virgins are typically found by a male after about an average of fifty minutes. Males also contact females prior to copulation. (Scott, 1986)

Edith's checkerspots prefer herb host plants from the families Scrophulariaceae, Valerianaceae, Plantaginaceae, and Caprifoliaceae. However, most populations of this butterfly are monophagous, and the preference is based on location. Egg-laying habits, larval host preference, and movements are locally adapted, and for that reason, the survival of Euphydryas editha depends upon the growing season of its host plants. The differences in host preferences are genetically based. Diet evolution in Euphydryas editha can be very rapid. Adult butterflies seek nectar and seem to prefer yellow or white flowers. The host plant flowers are never visited, apparently because the butterfly's proboscis is too short. (Cohen and August 31, 1996; Osborne and Redak, January 2000; Radtkey and Singer, April 1995; Scott, 1986)

Checkerspot butterflies have developed defense mechanisms to prevent predators from attacking. Larvae twitch in unison to repel predators, and, depending on the host plant of the population, the larvae, pupae, and adult butterflies are somewhat poisonous to vertebrates because they may injest toxins from the plant. (Scott, 1986)

Populations of Euphydryas editha use several different hosts to house and feed their pupae. Though they usually do not pollinate the flowers of the host, larvae have been known to eat the leaves, the flowers, and sometimes the entire host plant, and have starved trying to find another. (Radtkey and Singer, April 1995; Scott, 1986; Thomas, Singer, and Boughton, December 1996)

Edith's checkerspots lay their eggs on various plant species, sometimes resulting in the death of the host plant, which could be economically important to humans.

Larvae, pupae, and adults are poisonous to vertebrates if ingested. (Scott, 1986)

In order to obtain nectar, adult Euphydryas editha sometimes pollinate various flowers in the area of their habitat. (Scott, 1986)

Euphydryas editha populations mirror the changes in climate over long periods of time. Global warming is expected to eliminate the butterflies in the south, where the season is short and growing shorter. About three-fourths of the populations living in the lowest latitudes have become extinct. In Canada, however, less than twenty percent have disappeared. The sedentary checkerspots remain at their original habitat despite human interferences, and evolve adaptations to deal with these changes, thus making them dependent on the continuation of the human interference. This dependency results in insects that refuse to accept their ancestral host. In January of 1997, the subspecies Euphydryas editha quino and Euphydryas editha bayensis received federal protection under the Endangered Species Act. Euphydryas editha bayensis has also been given the Nature Conservancy Global rank of T1, which means that there are very few individuals remaining. (Cohen and August 31, 1996; Osborne and Redak, January 2000; Singer et al., 1993; Struttmann, 2004)

In the past thirty years, Edith's checkerspots have suffered two major crises. In 1967, humans cut down patches of a forest inhabited by the butterflies. The butterflies were able to adapt, and began to lay eggs on a new host with a high rate of breeding success. In 1992, a severe summer frost killed the new host, and checkerspot larvae starved. At least 21 subspecies of Euphydryas editha exist. (Miller, 1992; Thomas, Singer, and Boughton, December 1996)