Eastern tent caterpillars don’t need to be Democrats or Republicans to be part of the big tent party. They make their own fete in their silken shelters built in the crotch of tree branches. It is hard not to notice the collective squirming of hundreds of hairy crawlers, and easy to be repulsed by them.

These tent caterpillars are notable for these sturdy structures that can grow up to a foot long and quite wide. Little by little, as the caterpillars grow, they add silk to these tents, so it will accommodate their broadening bodies, and each tent can hold hundreds of growing caterpillars during their six-week life as caterpillars!

Eastern tent caterpillars are sun-lovers, orienting their tents facing southeast to take advantage of the morning rays. These tents act as mini-greenhouses providing for thermal protection against the cold spring nights. Their preferred trees include cherries and apples, but these caterpillars will also settle on other varieties.

Their habits are decidedly diurnal, since eastern tent caterpillars feed three times a day. Generally, the caterpillars will move army-like in a giant mass to remote parts of the tree to eat and then return at the end of the day to cozy up into their tents for the night. Thus, if you want to remove them from your flora, do so at night rather than during the day if you want your efforts to succeed.

The adult form of eastern tent caterpillars, also known as, Malacosoma americana, is called a lappet moth. The flying form is a nondescript moth that emerged from a cocoon spun by one of those calamitous caterpillars. The moth begins the cycle by laying egg masses on your trees that have up to 350 eggs in the summer and fall. These eggs overwinter and hatch after the buds break on their host tree.

Identify the eastern tent caterpillar by the distinctive white stripe that goes down the back of its body. The forest tent caterpillar is somewhat similar, but it has white dots or ‘footprints’ instead of a solid stripe. Another pest, the fall webworm, also makes similar tents, but the webworms make their webby enclosure at the end of branches rather than in the crotches of the branches. The webworm will also incorporate foliage in their silken constructions.

There are a few ways to get rid of these creepy crawlers. Some folks will use insecticides, however this method is not effective when the caterpillars are mature as they are now. As a child, I recall minor evening bonfires filled with web-covered branches and caterpillars and remember thinking it was quite disturbing that they were being burned alive. Perhaps that is how I got my start protecting wildlife.

And though entomophagy (eating of insects) seems like a reasonable answer to the problem, I could find no one brave (or crazy) enough to taste this species. Nor should you feed them to other animals. The eastern tent caterpillar is known to be toxic to horses.

Lucky for us, eastern tent caterpillars are univoltine. That is a fancy way of saying that they have only one generation per year. Soon enough, those tents will become empty as each full-grown caterpillar creates a cocoon to house it before making the big change into a lappet moth.

That can’t happen soon enough for me, as those tents are both destructive to the trees and an eyesore to boot. The moths that will emerge from the cocoons created by the caterpillar will be just about imperceptible, flying through the night, and starting the cycle all over again and getting ready for another spring of our tree’s discon-tent. 

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature.