Termites use mothballs in their nests.

Formosan termites may not worry about moth holes in their sweaters, but they are the first insects discovered to fumigate their nests with naphthalene.

People use the compound to rid human nests of carpet beetles and clothes moths and to repel intruders such as bats and starlings. However, naphthalene does not seem to bother Formosan termites, says Jian Chen of Louisiana State University Agricultural Center in Baton Rouge. In fact, they introduce the chemical as they construct their nests. In the April 9 Nature, Chen and his colleagues describe exposing Formosan termites to enough naphthalene to knock out a fire ant. These concentrations were higher than those naturally present in nests, but "there was no visible effect on termites," Chen says.

The termites, native to China, have spread to 11 U.S. states, mostly in the South. The insects build underground galleries from chewed wood cemented with saliva and excrement. This cement, called carton, contains naphthalene. It diffuses through the underground tunnels, perhaps as a defense against microbial infections and predatory ants.

Where in the world do the termites get the naphthalene? "We don't know the origin," Chen says. Some termite food might contain it, or an organism in the termites' nests might produce it from the cement. Naphthalene is not unknown in nature, he observes. Other researchers have found the compound in certain magnolia flowers and in the forehead region of male white-tailed deer.