SAN ANTONIO (Hearst) - Swarms of honeybees and moths housed in a big mesh-covered tent here might hold the key to finding nuclear weapons.

For three years, scientists at the Southwest Research Institute have worked with the insects to sniff out explosives under a Defense Department contract.

The scientists also are experimenting with rats, said Walter Downing, the institute's executive vice president.

But the technology still is in the experimental stage and has not been deployed in Iraq. Using bees clearly has limitations - the insects could not survive in desert-like conditions or extreme cold.

For now, the military must rely on people to track down weapons.

The institute has sent four researchers to Baghdad to help find unconventional weapons, and it plans to send four more people in a few weeks, Downing said.

The San Antonio institute, founded in 1947 by oilman and rancher Tom Slick Jr., had revenue of $339 million in 2002 and employs 2,800 people. Because of the nature of its contracts, it is difficult for the institute to talk about its work, so it keeps a low profile. But it is well known in scientific circles worldwide.

Southwest Research Institute's for-profit subsidiary, Austin-based Signature Science, has six people in Iraq working on detecting Iraqi weapons. The teams work with detection devices to track down explosives in the field, said Adam Hamilton, the company's chief executive.

In the insect experiments, the bees, moths and rats ferret out explosives spiked with sugar. Researchers at the University of Montana have been training the insects, and the San Antonio researchers have been helping conduct the studies.

Using bees to root out explosives is fast, cheap and relatively easy, according to a research paper by Jerry Bromenshenk, professor of entomology at the University of Montana.

Originally, the bee project involved searches for land mines but it was expanded to search for other explosives.

Bees have better sensors than humans and they make looking for land mines a lot easier than searching "inch by inch with a knife," according to Bob Cartledge, a consultant with the Pentagon's Advanced Research Projects Agency.

(Hearst News Service stories are distributed by The New York Times.)