Invertebrates
Eastern Tent Caterpillar
Malacosoma americanum · also called eastern tent caterpillars
In the fork of a cherry tree branch, a silken tent bulges with hundreds of eastern tent caterpillars, siblings from a single overwintered egg mass that will spend the coming weeks slipping out to feed on nearby leaves before returning to the shared shelter each time.
Overview
The eastern tent caterpillar, Malacosoma americanum, is a communal, tent-building insect native to forest and orchard habitat across a broad range of eastern North America. Its distinctive shared silken shelter, pheromone-guided foraging trails, and periodic population outbreaks make it one of the more behaviourally cooperative caterpillar species found in North American woodlands.
A caterpillar that never goes it alone
Unlike many solitary caterpillar species, the eastern tent caterpillar spends its entire larval life as part of a tightly coordinated sibling group, sharing a home, laying trails for each other, and even basking together on the same silken tent.
Status
Least Concern, widespread and common across suitable forest and orchard habitat throughout eastern North America, with population numbers that fluctuate naturally from year to year.
Eastern Tent Caterpillar: common questions
Why does the eastern tent caterpillar build a tent?
This species constructs a silken communal tent in the fork of a host tree's branches as a shared shelter for hundreds of siblings hatched from the same egg mass, offering protection from predators and weather between the group's regular feeding excursions across the surrounding foliage.
How do eastern tent caterpillars find their way back to food?
An individual caterpillar of this species lays down a combined silk and pheromone trail while returning from a feeding site, a chemical and physical marker that allows other members of the colony to more efficiently locate the same productive food source afterward.
Do eastern tent caterpillars kill the trees they feed on?
Rarely; while populations of this species can occasionally reach high enough numbers to noticeably defoliate a host tree in a given year, healthy trees generally recover and refoliate, meaning serious long-term damage from this species alone is uncommon.
When do eastern tent caterpillars hatch?
This species hatches in early spring from a single dark, foam-covered egg mass laid on a twig the previous summer, with the entire resulting tent colony descending from that one batch of overwintered eggs.