Little armies marching. Tiny feet stepping. Munching, munching, munching.

What is this stuff, anyway?

Moving into a new apartment could be simple. First you leave all your things in a friend's basement. Then you house-sit for someone for a month while you're looking for a cheap place to live. Finally, when you've located something suitably dark and roach-infested, you pull up to your friend's house in your station wagon and retrieve your belongings.

Easy, right?

Surprise Surprise Surprise

You start to pick up the ol' armchair, the one that's slightly grease-stained but more or less intact that you bought for $2 at the Lions Club auction in Thurmont, Md. Somehow, it looks different. It's out of focus. It's furry. IT'S COVERED WITH GREEN FUZZ.

And you get some of whatever-it-is on your hand and it's slimy and gooey and it smells. It's on the chair, it's on the sofa, it's on your pillow. The leather band on your wristwatch -- the one you left in your desk drawer because the hands fell off -- looks like it belongs in the rare-specimens section of the botanical gardens.

Welcome to Mildew City.

It's enough to make you wanna die.

Along with gutter rot and Ronald Reagan movies, mildew is one of the most disgusting things on this earth. Not only is it green and sticky and smelly like the wrath of God, it is alive. It spreads. It may even be listening.

Each year different groups have conventions in Washington. This year it was the Order of the Green, the International Brotherhood of Mildew. There were so many mildews milling about in Washington basements this summer that people who sell dehumidifiers ran out.

"You could lay your life on the line and not even get anybody to give you a hint where to find one," said Mike Ruhl at Reliable Appliances in Rockville, Md. "I've had more calls for them in the last week than I've sold all season."

Three weeks ago, there was one dehumidifier left in the Washington area. It was at the Sears Roebuck store in Bowie, Md.

Short of buying 5,000 chameleons and turning your basement into one of the few terrariums on your block with a dartboard, you can deal with mildew and still live in your house.

First consider ordering a dehumidifier now so you don't have to drive to Bowie next year. Several companies make them, such as General Electric and Whirlpool, and they cost anywhere from $110 to more than $200 in department and household-appliance stores. Mildew loves humidity. It stands to reason that it (they?) hates dehumidifiers.

Almost forgot. If you have an air conditioner, go turn it on. Quick. Even before you finish reading this story. Air conditioners are the ultimate dehumidifiers (as long as they're slightly undersized for the space so they work hard all the time; an air conditioner that is too big won't do as good a dehumidifying job.)

Dehumidifiers work like air conditioners. They suck up the air in the room, condense the moisture in it and dribble the water out somewhere.

Some models dribble right onto the floor.This is fine if you can move the machine next to the floor drain. If you don't cherish the idea of installing a sump pump for your dehumidifier because you don't have a drain, they buy one that drips into a bucket. Bucket capacities range from around 14 pints to more than 40 pints. A 20-pint unit is supposed to handle a normal-sized basement.

Avoid further flooding by purchasing a bucket dehumidifier with an automatic shutoff, one that doesn't runneth over.

One of the things the U.S. Department of Agriculture (USDA) does is think of ways to get rid of mildew. The mildew man at USDA is Leon Segal, a research chemist at the agency's Southern Regional Research Center in New Orleans, La.

"Down here in New Orleans, we have this [mildew] all the time," says Segal."It's a constant battle."

Segal is updating a USDA publication, last reprinted in 1976, called "How to Prevent and Remove Mildew" (HG-68, available by writing the Publications Division, Office of Government and Public Affairs, USDA, Washington, D.C., 20250).

If you already have mildew, says Segal, "you're getting into a nasty little situation." Mildew lives, breaths, eats and makes baby mildew [spores] like mad. You must get it out. Segal recommends first that you move everything to dry ground, such as outside in the sun. Go over upholstered furniture and rugs with the vacuum. Then apply a fungicide.

Hardware stores sell several products formulated especially to fight mildew. They come in spray applicators and as condensed liquid for $2- $3 a bottle.

Slipcovers and some clothing items should be washed. You can fight the mildew with chlorine bleach. (Be sure to use it only with items that can stand bleach.) Some vinegar added during the rinse cycle will help remove the chlorine smell. You may have to take some pieces to the dry cleaners. Try a mixture of lemon juice and salt for spots on nonwashable items.

Segal says the New Orleans mildew is so ferocious it even attacks paint made with mildew inhibitors. To remove it, he recommends a washdown with a tri-sodium phosphate mixture, or other fungicide, then a bath with a bleach-and-water solution to help keep it from coming back.

Mildew also feeds on the grout between bathroom tiles and will grow on shower curtains. Use a mixture of about one cup of chlorine bleach to a gallon of water, a brush and elbow grease on the tiles. You can add some tri-sodium phosphate to beef up the brew but never mix bleach with amomonia. This can result in toxic fumes and small explosions. Take the plastic shower curtains outside and scrub them on the driveway.

Be sure to wear rubber gloves and even eye protection. To prevent mildew's return in the bath, use the exhaust fan and the heat lamp.

Mildew leaves blotches. These can be especiallly disheartening if they appear on your Mies van der Rohe leather sofa. Segal's method of getting mildew off leather is to apply rubbing alcohol and perhaps some saddle soap. The alcohol may take off some of the wax and dye.

If you can't find a dehumidifier, Segal suggests heating the room with a space heater. Sounds crazy, yes. But warm air absorbs moisture. After the basement has been sufficiently sauna-like, open the windows and blow the air out with a window fan.

Some hardware stores also sell moisture-absorbing packets. These bags or small boxes or trays are filled with such moisture-attracting substances as silica gel, and are made to hang, for instance, in a closet. They cost anywhere from $3 to $6.

If you are storing clothes and things in an area that might be susceptible to mildew, make sure closet doors and chest lids seal tightly. For a dollar or so you can pick up a roll of foam strip with adhesive backing that will help make doors and lids seal more snugly. In an enclosed space, a lightbulb left burning will help keep down the relative humidity.

In any event, don't panic. True, mildew will grow on anything organic. But even if it gets on, say, a pants leg, you can brush it off. Like this: brush, brush, brush. It's more a problem on the arms and around the neck. GET OFF. Any higher than that and you are definitely in -- Aaiiiieeeeee -- trouble.