Recent reports that cities like Los Angeles, New York, Miami and Atlanta have roach problems don't surprise many. Roaches are an age-old problem, and they don't seem to be going away.

"Roaches have survived for more than 300 million years," said Paul Guillebeau, an entomologist with the University of Georgia Extension Service. "They have changed very little, according to fossil evidence."

A study by Combat Insect Control Systems ranked Atlanta as the 12th most cockroach-infested city in the nation. Los Angeles topped the list. The study was based on 1996 sales of roach control products.

Roaches come in more than 3,500 varieties. But you can tell most from other bugs by their flat, long, tinny, oval-shaped, brown bodies. The adults typically have wings.

"The most common varieties in the United Sates are the German, brown-banded, American, Oriental and smokey brown cockroaches," Guillebeau said.

They range from about a half-inch for German cockroaches to two inches for smokey brown adults.

"You usually find larger populations in cities," he said, "due to the number of apartment buildings. And the climate has some effect."

Cockroaches need three things to form a population: food, moisture and shelter.

"Apartment buildings usually provide all of these," he said. "Once a few get established, it doesn't take long for a huge population to form."

So how do you keep a population of roaches from taking over your home?

"Be scrupulously clean," Guillebeau said. "Even a crumb is a feast for a cockroach."

He recommends cleaning the kitchen every night and putting away all food, including pet food. "Roaches like pet food as much as your pet does," he said.

He also warns you to quickly fix leaks in the kitchen or bath, because even small amounts of water will attract roaches.

Some factors out of your control, such as climate, attract roaches, too.

"Some roaches come in from outdoors, like smokey browns, and they like warm climates," Guillebeau said. "Others like German cockroaches live almost exclusively indoors, and the outdoor climate doesn't matter to them."

To help get rid of roach populations, some new roach baits are now on the market.

"They're very effective, so you may not need to use as many pesticides as we once did," Guillebeau said. "However, if you already have a large roach population, you'll probably have to spray some kind of pesticide."

Remember when you spray that roaches like crevices. They prefer for their backs and legs to touch the surface at the same time.