The caterpillars leave their tents three times a day to feed.
By Karl Anderson
Tent caterpillars are hairy and dark-colored, with a white stripe down the back and a row of blue dots along each side.
It's easy to identify them by the "tents" they make on their host trees. They are the larvae of the tent caterpillar moth, a small brown insect marked with two vague diagonal white lines on each wing.
They emerge together in the spring from eggs laid the previous summer, and they immediately begin secreting the silken tent in which they shelter at night and during bad weather.
The tent is the product of the combined labor of all the caterpillars in a brood. It is built to face the morning sun, which helps the caterpillars warm up at the start of each day.
It is constructed of several layers of silk, with spaces between them that vary in temperature and humidity. This allows the occupants to move around within it and select optimum conditions for activity, growth and digestion. As the caterpillars grow, they continually enlarge their tent.
Weather permitting, the caterpillars leave their tent three times a day to feed, as a mass exodus first thing in the morning, in early afternoon, and just after sunset. Like ants, they lay down scent trails which they and their nest mates can follow to travel back and forth from food source to home.
After eating, they return to the tent to rest and digest their food. They complete their development in about eight weeks, eventually reaching a length of about two inches.
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They then leave the tent and seek individual protected places in which to spin their cocoons. They emerge as adults in about two weeks. Males may live for a week or more, but females die after they lay their eggs, which is usually within a day or two of their emergence.
The eggs are laid as a shiny, black, oval mass about half an inch long, wrapped around a small twig of a host tree. They are easy to find and remove in the winter, if one is so inclined. Each egg mass may contain 300 or more eggs.
The preferred host tree is the wild black cherry. A colony of these insects can defoliate a small tree in their two months of activity. But this is a native insect, and the native tree upon which it feeds is adjusted to its presence and soon grows new leaves. This may not always be the case with non-native domesticated trees such as apple and peach, which are also fed upon.
Few birds will eat tent caterpillars, but the caterpillars are prey to a variety of small parasitic wasps that lay their eggs on them.
The wasp larvae bore into the caterpillars and literally eat them alive. And the crowded conditions in their tents facilitate the spread of diseases.
As a result, tent caterpillars are somewhat cyclic in occurrence -- a year of great abundance is often followed by a few years of relative scarcity.
For information about the Gloucester County Nature Club, see gcnatureclub.org/.
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