Friday, July 23, 2010

Botanical Arsenic and Old Lace

Take a few minutes to watch this amazing time-lapse video by JCMegabyte. It covers the entire life cycle of the Pipevine Swallowtail butterfly. Video footage is courtesy of JCM Digital Imaging.

Plants have a fascinating variety of strategies to defend themselves against herbivores, including ourselves. If a species is to survive in the wild it needs thorns or spines, or armor, such as thick bark or nutshells. One of the most intriguing is the use are the poisons plants manufacture and concentrate in their leaves or seeds. Sort of like a botanical Arsenic and Old Lace

Of course, Aunts Martha and Abby used elderberry wine with cyanide, while Pipevine (Aristolochia macrophylla) leaves contain a toxin called aristolochic acid. If you were to eat enough of it, it could be fatal. This is the plant that Pipevine Swallowtails require in their larval stage. How can a small caterpillar thrive on a plant that could kill great big humans? Co-evolution my friends—eons of it. The caterpillars are able ingest the toxin without any ill effects, making both the larva and adult taste terrible. Birds and other predators learn to avoid them.
Aunt Martha: One of our gentlemen found time to say, How delicious!”

The larvae are black, with hornlike protuberances of orange or red. They also like to hang out in gangs, which is actually pretty intimidating to see if you don’t know what they are. The bright orange spots set off by blue on the adult are warning colors too. Kenn Kaufman and Jim Brocks book, Butterflies of North America, lists 6 other black butterflies of the Midwest that gain protection by mimicking the Pipevine Swallowtails coloration. The colors are effective for me too. I’ve never been tempted to eat a Pipevine Swallowtail.
Late instar of Pipevine Swallowtail caterpillar, on pipevine of course!

No comments:

Post a Comment