You may have noticed branches covered in these strange structures (Figure 1) during the spring, typically in March. These are tents constructed by eastern tent caterpillars, the larval stage of a Lasiocampid moth—a hairy and golden-brown colored moth with two white bands on the forewings. They spin their silk around tree trunks or branches to create a protective barrier against predators. The caterpillars congregate inside their tents to rest after feeding or to molt (Figure 2). They will emerge to feed on nearby leaves of their host tree. Usually the larvae will build their cocoon inside the tent.
The fall webworm larvae, caterpillars of some Erebid moth species (adults have hairy bodies and are all white or white with brown patches) also construct similar silk tents around host plants. These caterpillars typically form tents around the ends of tree branches, such as on oak, mulberry, and hickory, beginning in May to August.
Figure 1. Silk tent made by the eastern tent caterpillar, Malacosoma americanum. Photograph by Lyle Buss, University of Florida.
Figure 2. Eastern tent caterpillars, Malacosoma americanum, surrounding their silken tent. Photograph by James Castner, University of Florida.
Due to the eastern tent caterpillars’ feeding habits, they can be detrimental to the health of the tree. Since the caterpillars feed on leaves, during outbreaks they can defoliate their host tree: cherry, hawthorn, wild plum, and various other tree species. Luckily, the tree tends to survive, and might just experience less growth (with branch and leaf loss) than if it had not been the host of the caterpillars.
These caterpillars are not the only creatures capable of building webbed structures on trees in Florida. Webbing barklice can also make silken webs over branches and tree trunks in live oak hammocks and cabbage palm stands.
To learn more about eastern tent caterpillars, click here!