Butterfly Expert Comments on Journal Article
In reference to Nancy Hill’s article about Pawpaws and Zebra Swallowtails in the Spring 2013 INPAWS Journal, a few comments–
1. Some butterfly larvae can be cannibalistic when reared together in small containers. They may or may not be cannibalistic in the wild, especially when the eggs are laid singly (as in the case of Zebra Swallowtails), at a good distance from each other on a tree. I have seen numerous mentions of the cannibalistic nature of the larvae of Zebra Swallowtails on the internet and in a few books, but none that I have seen mention the source of the information, and whether the cannibalism was observed in captivity or in the wild. I have not found an eye witness account that describes this behavior in the wild. If Nancy has, I would be very interested in reading it.
2. A butterfly does not “spin a cocoon and become a pupa.” The terms “cocoon” and “pupa” are generally used to describe the “resting” stage of moths, while “chrysalis” is used for the resting stage for butterflies. Although many lepidopterists use “pupa” for both moths and butterflies, I have not seen the term cocoon used for butterflies. The “cocoon” of moths is a protective layer of silk which the larva spins around itself prior to shedding its skin and becoming a pupa. A swallowtail larva, on the other hand, does not spin a layer of silk around itself. It just lays down a small patch of silk on a firm substrate, such as a leaf, stem, or branch. It then attaches the end of its body to this silk button, and then spins a thin silk girdle, a sort of “safety rope” around its body. Then it releases its grip on the substrate, and hangs there, anchored by its attachment at the silk button and supported by the girdle. It hangs there for a day or two, then sheds its skin, revealing the chrysalis.
3. There are three forms of the Zebra Swallowtail. The first appears in early spring and has short tails and a considerable amount of red on the upperside of the wings. The second, which appears a few weeks later, have slightly longer tails and slightly less red. These two spring forms emerge from hibernating chrysalises. The third form appears in the summer, and has longer tails and even less red. Individuals of this form are offspring of the first two forms.
4. I believe the only butterflies that can actually digest pollen are tropical Longwings in the genera Heleconius and Laparus. Both genera are members of the Nymphalidae, or brushfoots, and are not swallowtails. Furthermore, I am certain that Zebra Swallowtail adults do not live for six months. If they did, worn adults of the spring forms would still be seen when the summer forms were flying. I have seen hundreds of Zebra Swallowtails in Indiana and have never seen any overlapping of the forms.
Sincerely,
Jeff Belth
Bloomington, Indiana
author of Butterflies of Indiana: A Field Guide