Chances are that if you’re on a camping trip in the New England woodlands this time of year you won’t be the only one pitching a tent. Eastern tent caterpillars, the larval stage of the moth Malacosoma americanum, have been out in full force this spring. Last year, two to three hundred eggs were laid by individual mother moths in the late spring and early summer, at which point the caterpillars developed and laid waiting until this spring to eat their way out of their eggs and into the world. The moths will only lay their eggs on trees that are members of the Rosaceae family, which includes cherries and apples.
The caterpillars are social, proceeding to build a silky layered tent after emerging from their eggs. The tent serves as a home base where caterpillars retreat between feedings. They often take on home improvement projects, expanding as they grow, adding layers to their tents throughout their larval lives. Once they are prepared to metamorphose, the brothers and sisters separate to construct their cocoons solo.
Tent caterpillars are wonderful architects, constructing their tents in the crotches of trees and saplings with the biggest wall facing southeast to capture peak morning sunlight. As they add layers to their tent, they can regulate their temperatures by going towards the innermost layers for warmth or the outermost layers to cool off. While tent caterpillars are considered pests on ornamental trees, the trees will recuperate after the larval stage is complete and they are no longer feeding as a group. To find Eastern tent caterpillars, look for their tents in the crotches of trees in the spring and early summer throughout New England and the eastern US, especially in woodlands and orchards.