Photo by Drees. Photo by C. L. Cole. 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. Each body segment is also marked with rows of black dots. Adults of the alfalfa caterpillar , Colias eurytheme Boisduval, are commonly seen sulfur butterflies. 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.