Visit the Arboretum this week, and you are likely to spy flowering dogwood trees, pink lady slippers, sunbathing turtles, and…an astounding number of eastern tent caterpillars emerging from their silken homes. Just what’s behind this exodus?
In early spring, an adult tent moth (Malacosoma americanum for those who like their Latin) lays 200 to 300 eggs in a single batch. Within three weeks, fully formed caterpillars rest within the eggs, where they remain until the following spring. The caterpillars hatch in tandem with tree bud development and immediately begin to build the silken tent that shelters them in the weeks ahead.
While these moths-in-the-making can’t be classified as social butterflies, eastern tent caterpillars are an extremely social bunch. The caterpillars emerge en masse from their tent three times a day to feed and add more silk. They return to the tent for protection and sunbathing: in most cases, the broadest wall of the tent faces southeast to better capture morning light.
After their final larval stage (tent caterpillars go through six) individual caterpillars leave the tent a final time to build cocoons of their own. The adult moths emerge two weeks later and are nocturnal.
Although tent caterpillars are considered pests due to their hunger for buds and leaves (black cherry trees, which are plentiful in the Arboretum’s meadows, provide a favorite meal), damaged trees usually recover and refoliate in a few weeks. This, coupled with the desire for a happy, well-fed bird population, explains the Arboretum’s official “live and let live” policy toward Malacosoma americanum.
by Jenny Houghton
Youth Program Coordinator