Re: What if a saddleback hasn't moved, is turning brown and shrinking?

Dear Mary,

Thank you for your question. I found it interesting to learn about all of the many reasons that your caterpillar might be shrinking, turning brown, and not moving. All of these reasons don't look so good for the continued life of your poor Saddleback Caterpillar. I suspect that your caterpillar is now dead.

But why is your beautiful caterpillar dead?

There are many infectious agents capable of killing a caterpillar. Many of these pathogens can now be grown in laboratories for use as a natural, targeted way of killing pest caterpillars. Caterpillar infections can be caused by viruses, bacteria, protozoa, fungi, nematodes, tiny wasps, and even a kind of algae. Some of the impressive list of pathogens are described on the website of Cornell University's Department of Entomology.

What can you do to make it safer for your caterpillars in the future? Make sure that the terrarium is not too wet. Many of the caterpillar parasites grow more rapidly when there is an abundance of moisture. The caterpillar will be able to obtain all the moisture it needs from the plants that it eats. Fresh leaves should be provided every few days and debris removed so that the caterpillar has access to all of the energy and moisture it needs to grow and develop. Finally, branches should be arranged inside the terrarium so that when the caterpillar is ready to pupate (build a cocoon) it will have a good spot ready to hang from. Other helpful suggestion s for rearing caterpillars in captivity are listed on the US Geological Survey's website.

Rearing caterpillars is an exciting hobby and a wonderful way to teach children about life. (You can look through many great suggestions that the University of Alabama at Huntsville has on teaching kids through the use of caterpillars in the classroom.) While most people I know try to stay away from Saddleback Caterpillars because of their potent venom, they are very pretty caterpillars to watch. Auburn University's Department of Agriculture has an excellent web site containing brief descriptions of commo n poisonous caterpillars with pictures, including the Saddleback Caterpillar, to look out for if you are seeking another caterpillar to bring into your classroom. There are also many species of caterpillar available commercially if the non-poisonous ones are hard too hard to find. (The non- poisonous ones usually try to blend into the background as much as possible, and can be very tough to spot in the wild.)

I do hope that you'll try again to rear caterpillars in your classroom. Now and then I find myself visiting a local elementary school to screen the children's heads for lice. (Yes, I think it's great fun!) While I poke through every terrified child's hair, I survey them to find out what their favorite insect is. Butterflies are the favorite by far! I can think of no better way to learn about the living world that to watch a caterpillar grow up to be a beautiful butterfly. (...or in the case of a Saddleback Caterpillar, into a pretty moth!)

I hope that you've found this information useful and interesting. If we can help you with any more information, please contact us again!


Sincerely yours,

John Carlson
MAD Scientist