It’s that time of year again around New York Harbor. Long, black fuzzy caterpillars with a white stripe down the back, and brown and yellow lines along the sides, are seeking a leafy meal.
The eastern tent caterpillar, Malacosoma americanum, have left their messy silken tents, often built in the crotches of tree limbs, and are now wandering everywhere - on walkways, on the ground, over plants, and in trees for food. They love wild cherry trees, which the New York metropolitan region has a lot of, apple, and crabapple trees too. They will also munch on the leaves of maple, peach, pear and plum. They emerge to feed on leaves in the early morning, evening, or at night when it's not too cold.
Though annoying to people, usually trees can tolerate a few caterpillar attacks. The little critters are native, and local trees have learned to deal with an onslaught of fuzzy tent caterpillars. A healthy tree or shrub can generally tolerate a total defoliation without suffering permanent damage. A tree will usually recover and put out a new collection of leaves before long. In the meantime, trees will look a bit bare by excessive defoliation.
But wild nature is not always pretty. Tent caterpillars are just doing what they have been doing for countless years, long before modern people came along and started squashing the poor critters on driveways, sidewalks, and courtyards.
Those hairy caterpillars will eventually become a reddish-brown moth with two pale white stripes lined diagonally down each forewing. Once the caterpillars are done eating and have enough energy, they will spin a cocoon. About three weeks later, out pops an adult moth. But most people never notice the little moth, as they emerge during late June or July when all the caterpillar action is over.
Moths, though, have an important job. They need to give birth to the next generation of tent caterpillars. They will mate and females begin to lay eggs in mass on small branches, between 150 to 400 eggs per branch.
The eggs will hatch next spring, when a new crop of fuzzy little caterpillars will emerge to wander away individually in search of protected areas to spin a cocoon. Caterpillars from two or more egg masses may unite to form one large colony. These insects are social; and a silk cocoon will act as a protected home for the petite caterpillars. During the heat of the day or rainy weather, the caterpillars remain within the silken nest to feel safe and snug as a bug in a silk rug.
Only one generation of eastern tent caterpillars develops each year. So enjoy the fuzzy feeding frenzy now, because it will not last long.