Large yellow Cloudless Sulphur (Phoebis sennae) butterflies are found in the entire eastern half of the United States as well as the southern part of the western United States.
Because they are large yellow active butterflies, Cloudless Sulphur butterflies quickly attract our attention in our gardens. Although they are considered yellow, many people consider them light green. When yellow scales are wiped off their wings, a yellow-green layer of scales remains. (Another large yellow butterfly in the southern US is the Orange-barred Sulphur.)
Cloudless Sulphur butterflies are found in almost all of the mainland United States. The extreme northwestern states would rarely, if ever, see this particular species of butterfly.
Their host plants are Cassia/Senna plants in the pea family. There are both wild ‘weedy’ and garden-invasive species as well as cultivated species of Cassia and Senna plants.
Many gardeners buy Christmas Cassia, Candlestick Cassia, or some of the other cultivated varieties and never notice caterpillars on the plants. The caterpillars are perfectly camouflaged. When they eat green leaves, they turn the color of the green leaves. When they eat yellow blooms, their body will change color to yellow.
Hatchling butterfly caterpillars are nearly microscopic. They grow thousands of times their hatchling size before they pupate.
Caterpillars normally rest along the leaf vein or leaf petiole/stem.
Adult butterflies are attracted primarily to red, orange, and purple colors. When they are in a yard, they’ll often dip down toward red lenses over car taillights.
Chrysalis colors will vary from yellow to pink to green to purple. Normally most will pupate on a plant and will be green. The chrysalis shape is much like a host plant leaf.
Chrysalises on black screen will be purple. Their chrysalis color depends upon the color of the items close to or on which they pupate.
Adult Cloudless Sulphur butterflies are also well camouflaged when they rest. They normally land on a leaf or item that is very near the same color as their wings.
The host plants, Senna or Cassia, are poisonous. Several species of host plants are greatly disliked by farmers. Growing in my Daddy’s squash, okra, and peanut fields in central Florida, Sicklepod Cassia was hoed, weeded, and a general headache to all of us who worked in the fields. When Daddy realized I was growing this plant on purpose, to feed caterpillars, he would just shake his head at me and grin. He would say, grinning, “I cannot believe you are growing that weed ON PURPOSE.”
Seed from many of these plants will remain viable for decades under the soil. When the ground is turned for a crop, seed that is turned close to the surface of the soil will sprout and grow, over 50 years from the day they first fell from the Cassia plant.