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Hunter: Fall Webworms

09/20/10 5:55PM By Edith Hunter
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(HOST)  Commentary Edith Hunter says that this time of year, many trees display what most people assume is the work of tent caterpillars - but probably isn't.

(HUNTER)  This is a year when we are going to see a great many fall webworms.

These are often confused with tent caterpillars but actually they are easy to tell apart. The webworms make their webs beginning at the tip of the branches and over the leaves on which they feed. They remain inside their tents feeding on the leaves that are there. The tent caterpillars make their silky tents in the crotches of limbs. They feed outside of their tents to which they only retreat when they are resting.

The eggs from which the webworms have hatched were laid by a small moth from late June to early July in clusters on the underside of the leaves at the tip of the branches. As soon as the caterpillars hatch in August they begin to make a web, and as they increase in size, they increase the size of their webs. The entire brood that hatches works together to make the web. They work downward from the tip of the branch until the web covers a large part of the branch.

The caterpillars hairy body is greenish to smoky black. Its sides have a yellow, orange and black pattern. The hairs are in clusters, and each cluster usually has one long hair twice the length of the other hairs. The hairs come out of small black warts.

Toward the end of August the caterpillars leave the trees and disperse. When they find a sheltered place, they spin their almost transparent cocoons. They will remain in their cocoons all winter and  spring, only emerging in late June and early July as small moths.  And then the cycle begins all over again, with the moths laying their eggs on the underside of leaves on any of over 100 forest hardwoods.  The fall webworms are not as destructive as are the tent caterpillars, but their webs, as they grow larger and larger, are not a pretty sight on our trees.

One of the old books that I have in my library "A Treatise on Some of The Insects Injurious to Vegetation," by Thaddeus Harris illustrated by Professor Agassiz, Published by Crosby and Nichols, New York, 1863, suggests that "the only time in which we can attempt to exterminate these destructive insects with any prospect of success is when they are young and just beginning to make their webs on the trees. So soon, then, as the webs begin to appear on the extremities of the branches, they should be stripped off, with the few leaves which they cover, and the caterpillars contained therein, at one grasp, and should be crushed under foot."

Unfortunately many of the webs on the Center Road are about thirty feet up, a little difficult for me to grasp.
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