Gypsy Moth

The European Gypsy Moth (Lymantria dispar) is native to.... That's right! Europe. There it evolved with all the nature that surrounds it and is not a problem. But in the United States, it is a major pest of deciduous forests.

The gypsy moth was brought to Medford, Massachusetts by Etienne Leopold Trouvelot in 1869. He wasn't trying to harm the trees - he thought he might be able to cross the gypsy moth with other moths found in New England and start a silk industry in the United States.

So what's a gypsy moth? It's small, only about an inch long, but look at those antennae! The feathered antennae are one of the distinguishing features of the adults. The adult males are a dust brown color like the bark of a tree and the females are larger and mostly white.

The female lays her eggs on trees then covers them with the tan colored hairs from her belly. The eggs hang out during the winter and hatch in the spring about the same time the leaves start to come out on oak trees.

When the eggs hatch, the caterpillars (or larvae) grow and molt through several stages. Each stage is called an instar.

Gypsy moth caterpillars can be distinguished from other kinds of caterpillars by the pairs of red and blue dots on their back.

The larvae form brown cocoons in the pupal stage.

Because gypsy moths have four distinct life stages (egg, larva, pupa, adult), we say that they go through complete metamorphosis.

It's the caterpillars. The caterpillars are so hungry as they grow that they eat leaves from all sorts of trees.

Oaks are their favorite. If there are a lot of gypsy moth caterpillars in one place, they can eat all the leaves off a bunch of trees.

This is called defoliation and can weaken the tree. If it happens multiple years in a row, it could cause the tree to die.

Because the gypsy moth isn't a native of North America, it doesn't have the natural predators and diseases here that keep population numbers in control like in Europe.

In the more than 150 years that the gypsy moth has been in North America, it has moved from Massachusetts into new areas. There's a point in southern Canada where the winters are too cold for gypsy moth eggs to survive, so it's mostly moving south and west these days.