eNature: Ask an Expert

Ask an Expert

caterpillar??

I live in So Calif on the coast. This afternoon I noticed that one of my birch trees had these caterpillers all over it. They are eating all of the leaves. The caterpillers are dark grey in color with red little spots down the center of the back and have red little feet. They also hang kinda upside down on the branches. Going thru the description of the different butterfly list I think it is the mourning cloak. Will they make the cocoon on the tree? If so how long does it take before they become butterflies? The tree will lose it leaves soon & What can I do to preserve and protect this process. I think it is pretty cool. Any info you can give me would be much appreciated. Thank you, Linda Hedell

First of all, let's get our terminology straight. Butterfly caterpillars don't make cocoons, only moth caterpillars do. If these are indeed Mourning Cloaks - and I think that's a reasonable call - they will make chrysales. When they're ready to pupate, they'll crawl 10-50 m to a sheltered spot such as the underside of a large limb or under an eave, to do so. The chrysales hang upside down and the butterflies emerge about 10-15 days later, depending on temperature. It's a natural process and should be allowed to succeed (or fail) on its own, without any "assistance" from you. You're likely to do more harm than good by trying to help, and it no longer would be a natural process.