Alabama Butterfly Atlas

Once called the Alfalfa Butterfly, Orange Sulfur's primary populations were based in the western U.S. where their host plant of choice was (predictably) alfalfa.  As eastern forests were cleared and converted to farmland, the alfalfa butterfly followed alfalfa’s eastward march, reaching Alabama in the 1930’s.  By the 1950’s, the state’s alfalfa crops were declining due to boll weevil infestations, but Orange Sulphurs were here to stay, having discovered a treasure trove of other acceptable legumes. Today, clovers and vetches satisfy larval nutritional needs and probably serve as primary host plants.

Orange and Clouded Sulphurs are closely related: their life stages look identical, and behavior is indistinguishable.  However, female sulphurs can choose appropriate mates because they are able to detect ultraviolet patterns that differ in the two species.  Orange Sulphur upper wing surfaces reflect UV light, while Clouded Sulphur wings absorb it.  Even so, hybrids reportedly occur. 

Both species often fly in the same habitats, creating a potential identification nightmare. Each produces white form ('alba') females, and these cannot be distinguished in the field.  Orange Sulphurs have some orange or gold on their upper surface, although there is less in spring-flying individuals. Clouded Sulphurs are lemon or greenish yellow on ventral and dorsal wings. They do not show orange or golden yellow above. Unfortunately, neither species sits with open wings, so the all-important field mark must be glimpsed in flight.

Orange Sulphurs fly throughout much of the United States. In Alabama, they are much more common in the upper two-thirds of the state.