The variable checkerspot, also known as the chalcedon checkerspot, is a butterfly in the mymphalidae family with the scientific name euphydryas chalcedona.
The variable checkerspot is usually brown-black with extensive yellow, red and white spots on the dorsal wing. The butterfly’s underside usually contains yellow and orange bands. However, as its name suggests, this insect is highly variable in appearance. Dorsal color can range from a brick-red background with brown and yellow markings in Sierra populations to yellow and black in northern Californian populations. Adult wingspan is 1.3 inches-to-2.2 inches.
The variable checkerspot is found in western North America, where its range stretches from Alaska in the north to Baja California in the south and extends east through the Rocky Mountains into Colorado, Montana, New Mexico and Wyoming.
Adult butterflies feed on nectar from flowers while larvae feed on a variety of plants including snowberry, symphoricarpos; purple owl’s clover, castilleja exserta; paintbrush, castilleja; chaparral honeysuckle, lonicera subspicata; buddleja; diplacus aurantiacus and scrophularia californica.
The butterfly’s habitat encompasses a large variety of environments, including sagebrush flats, desert hills, prairies, open forests and alpine tundra
During the breeding period, males congregate around larval host plants to encounter females. Males both perch near food plants and fly around them in order to look for females. Male butterflies do not stay in one encounter site for long and do not typically defend the territory of their encounter site. Males depend on visual rather than chemical cues to locate females.
Males court virgin female butterflies via physical displays. Females can play hard to get by flying away. Once a female moves to the ground or to vegetation, the male will persist in following her, succeeding only when the female remains motionless long enough for the male to effectuate coupling. The physical union between a male and female variable checkerspot typically lasts an hour but may continue for as long as six hours. The male provides unto the female during this encounter a nutrient-rich spermatophore as well as a mating plug that hinders the ability of females to mate with other males. This spermatophore left within the female’s bursa copulatrix, on average represents 7 percent of the male’s body weight.
Pregnant females look for host plants like diplacus aurantiacus that are close to nectar sources when they lay their eggs in clusters. The larvae that emerge from the eggs feed and live on these host plants, some of which have developed strategies to deter larvae from eating their leaves.
Pre-diapause larvae often move to fresher parts of the plant in which they are laid to secure a better food source. Before they enter diapause, the larvae leave the food plant to seek better dormancy sites such as under the bark of dead branches, in the hollow stems of dried weeds and in rock crevices. During diapause, some larvae are able to wake up and feed before re-entering dormancy
After diapause, the larvae emerge between January and March with pupation usually beginning in April. However, in high elevations, larvae can hibernate for several years. After pupation, the adult flight season begins between mid-April and May and continues into June. The adult variable checkerspot has a life span of around 15 days.
The variable checkerspot’s main predators are birds. In their evolution, the variable checkerspot has adopted a larval diet rich in iridoid compounds. Iridoids are chemicals produced by plants that bond to the plants glucose or sugar. Iridoids are bitter. Thus, scientists studying the variable checkerspot have observed birds quite often exhibiting head-shaking and beak-wiping behavior after killing a variable checkerspot, characteristic of tasting unpalatable prey.
In contrast to the herbivorous diet of the larva, the adult variable checkerspot’s main food source is the nectar it obtains from flowers.