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Tent caterpillars

06/11/03 12:00AM By Edith Hunter
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(Host) Early this spring commentator Edith Hunter noticed quite a few small white "tents" in her apple and wild cherry trees, so she decided to learn more about the life of the tent caterpillar.

(Hunter) We often confuse tent caterpillars and fall web worms. We shouldn't. The fall web worms, as their name indicates, appear in the fall, and make their webs over the tips of the leaves. The little Golden Nature guide illustrates both a tent and a web. The egg mass of the tent caterpillars is made up of several hundred eggs. Laid in the summer on the branches of the host tree, the eggs form a solid bracelet around the branch. This is covered with a thick protective coat of brownish varnish.

What I was really curious about was what the hatched-out caterpillars eat. They seem to remain in the tent where there is nothing to eat. My question was not answered by the Golden guide so I went to a wonderful book, A Treatise On Some Of The Insects Injurious To Vegitation, by Thaddeus William Harris, published in1863. I was sure that this book that I bought at the Vermont Antiquarian Book Fair one summer would answer all my questions, and it did. The19th century nature books were written for the general public by nature enthusiasts who spent a great deal of time in close observation. These books are often outstanding in their detailed descriptions and illustrations. This one was "Illustrated By Engravings Drawn from Nature Under The Supervision of Professor [Louis] Agassiz."

I learned that the caterpillars leave the tent daily and spin a thin silk thread as they crawl along. Like Hansel and Gretel's crumbs the thread leads them back home after they have had their fill of tender young leaves. "They come out together at certain stated hours to eat, and all retire at once when their regular meals are finished; during bad weather however they fast." This rainy May they must have done a lot of fasting! As they grow, the caterpillars enlarge the common tent.

As well as accurate colored engravings, there is a detailed verbal description of every stage of the insect's life, from egg to caterpillar to moth. The caterpillar leaves the tent permanently in early June and finds a sheltered place in which to make its cocoon. Two weeks later it emerges as a moth about an inch and a half in size, rusty brown marked by oblique straight dirty white lines. The moth lays its eggs in July on the host tree, and the cycle begins again.

I've been told that they're not especially harmful but the eggs may be removed easily by scrapping them off the branch, and the old book recommends thrusting a soapy mop into the tent to destroy it. As the book says, "Early attention and perseverance in the use of these remedies will reward the farmer with the grateful sight of the verdant foliage, snowy blossoms, and rich fruits of his orchard."

This is Edith Hunter on the Center Road.
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