Researchers have discovered a "social insecticide" that destroys termites by disrupting the social life among wood-chewing insects and preventing food from being distributed to the termite colony.

While there are effective chemicals to kill termites, they are toxic to humans, and must be used with special caution. The new insecticide being tested at the U.S. Forest Service laboratory in Gulfport, Miss., is a hormone, and thus might be safer to use in combating the estimated $750 million annual damage termites do.

Dr. Ralph Howard announced the new work at an American Chemical Society meeting in Normal, Ill., this month.

He reported that a synthetic termite hormone called methoprene was fed to the insects.

The hormone in normal amounts makes the termites, at the juvenile stage, molt and become one of the three different types or social castes among termites: a queen or king, which do nothing but reproduce; a soldier, which protects the colony, or a worker, which eats wood and supplies the colony with food.

But when too much of the hormone is given to the termites they begin to molt into outcasts, such as creatures with soldier heads and worker bodies.

The outcasts disrupt the social chain so that food does not flow normally from the worker to the rest of the colony. Within three to four weeks the termites die of starvation.

The excess hormone also kills some digestive organisms in the termite gut, so that wood cellulose cannot be digested, thus promoting mass starvation.

Joe K. Mauldin, an entomologist and project leader at the Department of Agriculture's Forest Service lab, said a commercial product using the hormone may be years away even if all obstacles to development are overcome.