It has become popular for butterfly gardeners to raise monarchs in protected circumstances on tropical or giant milkweeds and release them into the wild. It is much less common for other local butterflies to be reared in captivity. Gulf fritillaries and zebras require toxic passion vines for their caterpillars. The sulphur butterflies require cassias/sennas , which are also poisonous, as larval food. It is interesting that those butterflies that are food specialists have clearly developed evolutionary adaptations to not only tolerate the toxins, but often to sequester them and use them as a defense. It is unclear whether sulphur butterflies do so since their caterpillars are camouflaged and the adults fly very fast, both adaptations to reduce predation. Instead they have developed the ability to eat the poisonous cassia and thus have this food source to themselves, without competition from other butterflies.
While working in our yard on Manasota Key, I observed a large female orange-barred sulphur depositing eggs on our cassias. Since these only rarely succeed in developing naturally due most likely to predators, I collected a number of eggs on twigs of cassia and brought them into our sunroom. Raising sulphurs is more difficult than monarchs, since cut cassias dry out more quickly than milkweeds and provision of fresh food is thus somewhat difficult. The eggs hatched in about four days, and after about 14 days the large healthy caterpillars hung up in the “J” configuration. Soon thereafter the sulphur caterpillars shed their larval skins and transformed into the remarkable green chrysalis. After another 11 days the chrysalis matured and the male and female sulphur butterflies could be seen within. Shortly the butterflies emerged with wrinkled wings, pumped up their wings, dried them and flew away.
I have found sulphur butterflies to be spectacular inhabitants of our garden. Wasps eat most of our wild caterpillars, so the chance to rear them inside was a golden opportunity to learn more about them up close and personal. I highly recommend that you plant cassias in your garden to attract both orange-barred and cloudless sulphurs, the two large locally common species. These “flying flowers” are amazing and a close study of their habits will repay your time and enrich your garden experience. Cassias have bright yellow flowers and will also beautify your garden while expanding its ecological value.