Tuesday, June 21, 2005

Clever caterpillars

In the late spring and early summer, many trees will shed some leaves just as dieting humans shed some pounds – to lose a little excess, unnecessary weight. But not all the leaves sent to the ground are the tree’s doing.

Trees are home to countless caterpillars, the larvae of moths and butterflies that dine on leaves. And searching the leaves for caterpillars are scores of hungry birds. Many, like chickadees, will look for damaged leaves, sensing that where there are holes, there are caterpillars nearby.

As defenses against birds, some caterpillars taste bad, grow spines or hairs, or bear bright “warning” colors. But in one of the little miracles of evolution, many edible caterpillar species have developed a different defensive technique. When they finish munching on a leaf, they clip it off and let it fall to the ground so it won’t give away their location to a bird on the hunt.

They don’t cover their tracks, they drop them.

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