Early in the spring in the front range of Colorado (between the snowstorms) lives a small and easily overlooked butterfly. The Moss's elfin (Callophrys mossii) flies for only two to three weeks between late March (early years) and early May (late years). The adult butterflies have a wingspan of only 1 inch. The upper-side of their wings are a rich coppery brown, while the undersides are scribed with a white line and border in red. Their coloration is similar to their habitat and camouflages them in the area they call home.
These butterflies have small territories, measured in yards, in which they spend their entire adult lives. The males perch on twigs or rocks low to the ground and watch for mates. Females lay individual eggs on Stonecrop leaves (Sedum sp.).
Once the eggs hatch the tiny reddish to green striped caterpillars feast on the Stonecrop leaves, then flowers and fruits. When fully grown, the caterpillars pupate and spend the winter as chrysalids. When the warm rays of the spring sun return, the adults begin to fly again for a few weeks, unobserved by most humans.
Moss's elfin has a patchy distribution, occurring only where there is ample caterpillar food, especially in gullies with rocky perches. Colorado is the southernmost extension for this species down the Rocky Mountains, though it also occurs along the Pacific coast into southern California. This butterfly is on Colorado Natural Heritage Program's list of special concern species. Although it is considered stable throughout its entire range, this species is considered to be vulnerable to imperiled throughout Colorado.