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Tent Caterpillars

Les Harrison is the UF/IFAS Wakulla County Extension Director

Summer is a popular time of year for camping. As school ends, parents are busy signing their kids up for day and overnight camps. Tent moths have a similar plan in mind for their young.

Though their parents are long gone by the time they hatch, tent caterpillars are born to camp. Once they have set up in your yard, you may have a hard time getting them to leave.

These native caterpillars build large, thick nests in the forks and crotches of many kinds of trees–seemingly, the ones especially valued by the homeowner. The silky tent-shaped nests are easy to see and identity on the upper branches of host trees.

The caterpillars which emerge in the spring of 2015 were laid in the spring of 2014. The adult moth lays her eggs in a single batch in May to July. There are 200 to 300 eggs laid in the group.

The mass of eggs are shiny, reddish-brown and look like dried foam. They are ordinarily about six inches back from the tip of a thin twig in host tree.

In approximately three weeks, the eggs contain fully-formed caterpillars, but the small caterpillars remain in the eggs until the following spring.

In late-February to mid-March, they chew their way through the egg shells, ready to eat, as their host tree is entering the spring budding period with plentiful, tender vegetation.

The voracious larvae immediately infest and–if in sufficient numbers–defoliate plum, cherry and many others. Normally the trees recover after a few weeks, but weakened or diseased trees may die.

When not eating, the newly-hatched caterpillars construct their silk tent. The caterpillars use a pheromone trail to guild them back home when feeding is done.

A social insect, the eastern tent caterpillars congregate at their specific tent during the night and in rainy weather, expanding it to accommodate their growing size. These caterpillars do not feed within their nests, keeping it clean and neat.

The caterpillars disperse to colonize new areas when maturity is reached. They construct cocoons in protected places once they have sufficiently scattered.

Birds are not attracted to these hairy caterpillars. If they have a heavy concentration of black cherry leaves in their diet, the caterpillars will have a bitter, acrid, taste.

Parasitic wasps and weather are the two most common causes of caterpillar death. These caterpillars are especially susceptible to cold weather once they have emerged from their eggs.

About two weeks later, an adult moth emerges to begin the process again. Mating and egg-laying commonly occur within 24 hours of the moths emerging from their cocoons.

These brown moths are nocturnal and are encountered in flight only at night. They are an inch to two inches wingtip to wingtip at maturity, and easy to overlook.

Unfortunately, once they set up camp, they always overstay their welcome.

For more information on tent caterpillars and moths, view the EDIS publication, Forest Tent Caterpillar.

Contact your UF/IFAS Wakulla County Extension Office at 850-926-3931 or http://blogs.ifas.ufl.edu/wakullaco/ to learn more about Eastern Tent Caterpillars in Wakulla County.

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