Clouded Sulphur

The Clouded Sulphur is one of the most abundant and widely distributed butterflies in North America, a member of the family Pieridae found from coast to coast wherever clover and alfalfa grow. Its pale yellow color and clean black wing margins make it a familiar sight to anyone who has walked through a hayfield or roadside meadow in summer.

As a member of the genus Colias, it belongs to a group of sulphurs adapted to open, disturbed, and agricultural habitats, benefiting from the widespread cultivation of clover and alfalfa as forage crops. It frequently hybridizes and co-occurs with the very similar Orange Sulphur, and the two species are often seen flying together, sometimes producing intermediate-colored individuals.

Despite occasionally being considered a minor presence in agricultural clover and alfalfa fields, the Clouded Sulphur plays a beneficial ecological role as a pollinator of wildflowers and crop legumes.

• Medium-sized butterfly, pale lemon-yellow to greenish-yellow above with a solid black border on the forewing and hindwing in both sexes, though the border is more broken or reduced in females.
• A small dark spot is present near the center of the forewing, and a small orange spot marks the hindwing.
• Underside is yellow-green with a silvery, sometimes double-ringed spot on the hindwing.
• Females can occur in a pale white form in addition to the typical yellow.
• Very similar to the Orange Sulphur; best distinguished by the absence of orange suffusion on the upperwing (Clouded Sulphur stays yellow, not orange) and by examining the underside spot pattern.

This species is found across nearly all of temperate North America, from southern Canada to the Gulf Coast, in open habitats such as clover and alfalfa fields, meadows, roadsides, and vacant lots. It is especially common in agricultural areas where its legume host plants are cultivated. Adults fly from spring through fall, with multiple broods across most of its range, and are active on sunny days, often gathering at puddles or mud in groups.

Adults fly with a characteristic low, fluttering pattern over open fields, visiting a variety of flowers including clover, asters, and goldenrod for nectar. Males frequently gather at damp soil or puddle margins in a behavior known as puddling, thought to help them obtain minerals. Caterpillars feed on clover, alfalfa, and other legumes, are well camouflaged in green, and rest along leaf midribs to avoid detection by predators.

Eggs are laid singly on the leaves of clover or alfalfa and are spindle-shaped, turning from pale yellow to orange-red before hatching. The caterpillar is green with a pale side stripe, feeding on legume foliage and molting several times before pupating. The chrysalis is green and attached upright to a stem by a silk girdle. Multiple generations occur each year across most of the range, with the species overwintering as a partly grown caterpillar or chrysalis in colder regions.