Malacosoma americanum
The Basics:
- Size: caterpillars 2-2 ½” long when mature; moths with 2-2 ½” wingspans.
- Color: caterpillars are black with white stripe on back and series of blue dots on sides; moths reddish-brown.
- Habitat: frequently found on cherry and apple trees around the region.
- Where and when to observe: caterpillars active in spring on host plants.
The Details:
On spring days as leaves begin to unfurl, many of our city’s tree branches sport large, strange webs thanks to the work of a rather messy little insect, the Eastern Tent Caterpillar.
Eastern Tent Caterpillar, Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org
Soon after hatching, the larvae (caterpillars) begin to eat leaves and construct these silk tents, which may eventually cover the entire plant! And because they feed in groups, the hungry insects might devour all a tree’s leaves. But the feeding frenzy is certainly not one-sided as the caterpillars make a nice meal for birds.
The tents provide caterpillars with protection at night and from bad weather, and though rather unattractive, the young insect is anything but. Eastern Tent Caterpillars are black with a white stripe running along the back, and a series of blue dots on the sides. When mature in 4-6 weeks, they measure 2-2 ½” long.
Eastern Tent Caterpillars and tent, Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org
Larvae settle down on trees, fences, and similar structures to spin yellowish-white cocoons where they will rest and change shape to become moths. This adult form emerges in late June to early July and unlike the caterpillars, adults are comparatively bland in color — reddish brown bodies and wings with a white stripe along the forewing. Wingspans are 2-2 ½” long.
Eastern Tent Caterpillar adult, Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org
After mating, females lay up to 300 black eggs, clustered together. Since one of their favorite foods are cherry and apple trees, the 1” long egg clusters encircle a twig so the caterpillars don’t have far to travel when they hatch the following spring.
References:
- Eastern Tent Caterpillar/The Interactive Plant Manager by New York State Integrated Pest Management Program, accessed on April 3, 2009 at http://www.nysipm.cornell.edu/ornamentals/Eastern_tent_caterpillar.asp.
- Field Guide to the Natural World of New York City by Leslie Day, published 2007 by Johns Hopkins University Press.
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