Common Name: Cloudless sulfur
Scientific Name: Phoebis sennae eubule (Linnaeus)
Description: One of the larger sulfur butterfly species, wingspan of butterflies can be over 3 inches. Males are brilliant yellow above with no markings. Females have some black marginal markings. Caterpillars, 1 inch long when fully grown, are pale yellowish green with yellow stripes along their sides. Each body segment is also marked with rows of black dots.
Another subspecies, Phoebis sennae marcellina (Cramer), occurs in the Rio Grande Valley. Males are more patterned underneath with orange-brown and females have a warmer shade of yellow on the upper surface and a ground color of pinkish-orange on the underside. Thirty six species of Pieridae, butterflies called “whites” or “sulfurs” occur in Texas.
Adults of the alfalfa caterpillar, Colias eurytheme Boisduval, are commonly seen sulfur butterflies. Adults have a 2 inch wingspan and wings are yellow to orange-yellow with black markings along the wing margins (on males, markings are solid and in females, black markings are interrupted by spots). The caterpillar stages feed on leaves of alfalfa and soybeans, growing to 1-1/2 inch long with green bodies marked on each side with a thin white stripe in which a finer red line occurs.
Life Cycle: Adults overwinter in south Texas. Females lay eggs on host plants. Caterpillars hatching from eggs develop through several stages before forming a smooth chrysalis suspended from a plant stem by its base and a silk thread. Broods are continuous in the eastern half of Texas.
Habitat and Food Source(s): Caterpillars have chewing mouthparts. Adults have siphoning mouths. Larvae feed on wild senna (Cassia) species. In Louisiana, the primary host is the Partridge pea, Chamaecrista cinerea). During the day, they hide in a “tent” made of cassia leaves webbed together with silk. Adults are strong migratorsm, particularly in late summer when their range expands northward. Adults can be common as they visit flowers like thistle and morning glory.
Pest Status, Damage: Harmless, migrating species. No damage.
Literature: Howe 1975; Neck 1996; Wright 1993.