If you have ants, but they're pale gray or white, they aren't ants -- they're termites, and you have a problem.

Even if they are the dark brown or black color of true ants and, in addition, have two pairs of long, translucent wings of equal length, they are termites -- the kind that don't eat wood but who reproduce the destructive wood-eating pests.

The winged reproducers sometimes are confused with winged ants, says Dr. F. E. Wood, associate professor of entomology at the University of Maryland.

But, he adds, the flying ants' wings, unlike those of termites, are of uneven length and their waists are pinched in, as are those of the wingless ants. Termites' figures are solid and broad from head to abdomen. Wood said that termites cause more than $500 million in damage each year to buildings in the nation.

They do some good, though, by reducing dead wood, such as tree stumps, root and logs, into components of the soil by eating the wood cellulose. This exposes the wood to decomposition by weather and fungi.

In the Washington area almost all of the termite damage is caused by the eastern subterranean type. They live in underground colonies and emerge through tubes made of dirt and saliva to get to your house and back to theirs.

They usually enter a house through a crack. Where a wooden portion of the building is in direct contact with the ground, free meals obviously are made much easier.

Frequently a door stoop provides access. Termites can live under the stoop come up through the crack when the stoop has settled and pulled away from the house.

They also may appear around fireplaces and chimneys, cracks in brick veneer and rock foundations, and areas next to slab patios, walks and carports. v

Property owners who have made a study of the problem and know what they're about can control the insect invasion themselves, Dr. Wood said.

But failing that ad if special tools are needed, the best bet is to call in a pest control professional.

The first thing a do-it-yourselfer should consider, Wood said, is whether the house has a crawl space or a basement or a slab foundation.

Then the entry area must be pinpointed so that a barrier of insecticide -- usually chlordane -- may be placed in the ground between the building and the termite colony.

Here are the control methods for the various types of structures:

Buildings with crawl space foundations: Dig trenches six to eight inches wide adjacent to and around all piers or supports, and pipes, and along both the inside and outside of all foundation walls.

Where the footing is more than 12 inches deep, make crowbar, pipe or rod holes no more than one foot apart and extend them from the bottom of the trench to the footing. This will prevent termites from gaining hidden entry to the building through voids in these types of foundations. The trench should never be dug below the top of the footing or structural damage may ensue.

Pour the pesticide into the trench at the rate of four gallons per 10 linear feet for each foot of depth. If the trench is deep, apply the chemical to alternate layers of about six inches of soil.

Buildings with basement foundations: The method is similar to that for treating crawl spaces, but you only have to treat the outside. However, you must go deeper. To treat the soil along the outside walls of basements, dig a trench six to eight inches and a foot or more deep, adjacent to the wall.

Then make crowbar, pipe or rod holes, no more than one foot apart that extend from the bottom of the trench to the footing. Use the same rate in pouring the pesticide as used for crawl space buildings -- for gallons per 10 linear feet for each foot of depth from grade to footing, alternately replacing and treating six-inch layers of soil.

Some houses have both crawl space and basement foundations. The basement and next to the crawl space can be difficult to treat. But this must be done, Wood said.

Pay close attention to the raised door stoop. Be sure the soil adjacent to the foundation is treated. Do not go around the stoop. It is best to knock a hole in each side and clean to dirt and wood out. Then put louvers in the holes so the area can be dried out and checked periodically.

If no other method is possible, the stoop should be drilled along the side next to the house and the holes rodded down about eight inches apart.

Sometimes these stoops can be cleaned out by coming through the foundation from the inside of the house. A walk or carport directly adjacent to the building presents another problem. Holes then have to be drilled next to the building and rodded and treated.

Buildings with slab-on-ground foundations: It is difficult to treat the soil underneath the slab in a way to protect the wooden plate and wall studs.

Drill holes about one-half inch in diameter through the slab close to the points where the termites are, or where they may be entering. Space the holes about six inches away from the wall and about 12 inches apart to insure proper treatment of the soil underneath, taking care to avoid drilling into plumbing and electric conduits.

To help prevent re-infestation, in general, remove wood and other debris containing cellulose from under or adjoining buildings. Remove wooden items that connect to the ground with the woodwork on the exterior of the building. Chemically impregnate or treat around wood piers and posts that are to be driven into the soil.

Termites usually leave the house every 24 hours to return temporarily to their nests. When the poison is in the ground, they get hit with it on these trips.

Homes whose mortgages are insured by the Federal Housing Administration or guaranteed by the Veterans Administration must be protected from termites by physical barriers in the construction or by chemical barriers, such as treated soil or wood.

The District building code specifies that an "approved metal shield shall be placed around pipes and other appurtenances entering buildings through foundation walls or basement floors in interior locations that are not accessible."

The shield acts to seal off openings through which termites may enter. There are different requirements for the removation of existing buildings. In general, these cover wood treatment.

Northern Virginia and suburban Maryland have building code requirements which, in general, cover oil treatment, impregnation of wood, use of termite-resistant wood and distance from ground.

Bernard Koman, president of the Maryland Pest Control Association, believes homeowners would be well advised to call in professionals to battle the insects.

To do a proper job, he says, equipment is needed that can shoot a pesticide into the ground at 150 to 200 pounds pressure. Drilling tools also may be necessary, he says.

He gave a "ballpark" estimate of cost of $200 to $500 for the job, depending on the size of the area and the amount of drilling required. Jobs, he said, are guaranteed for a year. An "indefinite" warranty may be obtained for about 10 percent of the total job cost.

The University of Maryland Cooperative Extension Service publishes Bulletin 245, "Controlling Termites," which may be ordered by Maryland residents free of charge from their county cooperative extension service as listed in the phone book.

The Virginia Polytechnic Institute produces Cooperation Extension Publication No. 433, "Termites in the House." Fairfax residents may obtain it by writing to Cooperative Extension, 3945 Chain Bridge Road, Fairfax, Va. 22030.

Arlington residents should write to Cooperative Extensive, 2049 15th St. N., Suite 110, Arlington, Va. 22201.

Alexandria residents should write to Cooperative Extension, Room 311, City Hall, P.O. Box 178, Alexandria, Va. 22313.

A booklet "Subterranean Termites, Prevention and Control," Stock No. 001 -- 000-03948-2, may be obtained for $1.30 payable to the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

The University of the District of Columbia distributes the same booklet free of charge but has a limited supply, a spokesman said.