The sleepy orange is a common butterfly of open, sunny and disturbed sites throughout the southeastern U.S. where it is particularly abundant in the late summer and early fall. Although not implied by its name, adults are extremely active and have a quick, nervous flight. The sleepy orange has two distinct seasonal forms. Summer-form individuals have rich butter-yellow hindwings underneath, whereas individuals produced during colder months are tan to brick-red and more heavily patterned. The upper wing surfaces of both forms are bright orange with black borders. Females tend to be larger than males and are considerably less vibrant. Males often gather in large numbers at mud puddles.

Although primarily a southern species, the sleepy orange annually establishes breeding colonies as far north as the Midwest and Ontario, but is unable to survive extended periods of freezing temperatures. Along the warmer Gulf Coast, adults overwinter in a hibernation-like state called reproductive diapause. Females deposit their small white, cone-shaped eggs singly on the undersides of host-plant leaves. Mature caterpillars are bluish-green with a faint yellow or cream stripe down each side. When not actively feeding, the larvae rest on the top of host-plant leaves. The pupa (or chrysalis) may be green or black and is attached to a substrate by a silken pad at the base and a silken girdle around the middle. Like most sulphur butterflies, the pupae have a pronounced keel and an apical point.

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