In the Garden:
Upper South
September, 2003
Regional Report

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The cecropia caterpillar is a North American silkworm that grows up to be the largest moth on the continent.

My New Best Friend

How can you not fall in love with a 4-inch-long caterpillar with blue "feet," even if he is eating every leaf on a young persimmon tree? A neighbor and her 3-year-old son discovered him in our yard recently. A quick perusal of a field guide to North American insects and spiders identified him as a cecropia caterpillar, who one day would become the largest moth in North America. Each day we watched as he progressively defoliated the little tree.

A Colorful Transformation
Actually, he had help from a friend. Once they finished the persimmon and moved on to a nearby wild cherry seedling, I lost track of one. Even though cecropia caterpillars are almost 3/4-inch in diameter and 3 to 4 inches long, their pale, blue-green bodies readily blend in with their mealtime stems and leaves. More noticeable are the yellow, orange, or blue tubercles along the sides. After about two weeks or so of this voracious eating, the caterpillar will begin to spin a cocoon.

The cocoon will resemble a hammock slung just below a branch. The cecropia is one of a handful of native silkworms, which also include the promethea, polyphemus, and luna. The caterpillar will spend the winter snug in a silk -- rather than a down -- comforter, as the cocoon is composed of two papery walls of silk filled between with a loose matting of silk. At one end of the cocoon, the silk is spun lengthwise rather than crosswise, thus creating a valve through which the moth emerges in the spring. Once the cocoon is spun, the caterpillar sheds its skin and becomes a smooth, brown, oval pupa.

Next spring, about May, the pupa will transform into a moth that emerges wet and wrinkled. After drying off, it will stretch into a 5 - to 6-inch moth with dusky, gray-brown wings variously marked with white and terra-cotta bands and spots. The caterpillar is such a hearty eater that the moth never feeds, lacking a sufficiently developed mouth to eat even if it wanted to.

The moth's function, mostly under the cover of darkness, is to lay eggs, each of which will hatch into a quarter-inch-long, black caterpillar. In about four days, a caterpillar will molt, donning yellow-orange with black tubercles. Another week, and with the next molt, the caterpillar will turn yellow, to be followed in yet another five to seven days by an outfit of blue-green. One last quick change yields the final stage, of which I was witness.

For anyone who gardens or walks the fields and woods, this is just one of the myriad of miracles that surround us, if only we take the time to see. And it's just one more reason to be judicious in the use of chemicals in the garden. There are other persimmon trees to be had if this one doesn't make it.


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