As winter still chills the bones, spring seed catalogs are warming mailboxes everywhere.

Mixed with offers of amazing azaleas and zippy zinnias are more unusual items: bugs. Good bugs. Earthworms, ladybugs and nematodes.

Why buy bugs from a catalog?

"People buying predators such as lady beetles are often disappointed," said Beverly Sparks, a University of Georgia Extension Service entomologist.

"They buy them and release them in their garden area," she said. "And when they go back in 30 minutes the beetles are dispersed."

The problem is not getting these beneficial creatures into your garden. It's getting them to stay put.

"We recommend that people observe their garden and see if they have the insects there," Sparks said. "Then preserve them. Don't buy them and bring them in."

But the beneficial bug game is a real "Catch-22."

"It's a trick," Sparks said. "They're predators, so insects have to be around or the beneficial ones will leave."

If you don't have bad bugs, you probably won't have good bugs either.

If you have sprayed for insects using a lingering insecticide, you will also kill your beneficial insects.

Beneficial insects such as lady beetles are easy to spot. Nematodes, on the other hand, are much harder.

"There are plant-parasitic nematodes and insect- parasitic nematodes," Sparks said. "You won't necessarily see the nematodes themselves but can see evidence of them."

If you closely examine bodies of dead insects found in the soil, you may see the tiny parasitic nematodes.

"One problem with buying nematodes to use in your garden is that they attack most soil-dwelling insects whether they're beneficial bugs or pests," Sparks said.

You can test for an abundance of earthworms by digging through the soil. You should find either the worms themselves or the channels they dig. If you have good soil, you'll have earthworms. If you don't have good soil, earthworms won't stay even if you put them there.

To keep your natural supply of beneficial insects, remember that they need a supply of pests to feed on.

"If they don't have a ready food supply, lady beetles will fly away," Sparks said. "Nematodes naturally occur in the soil and can't move great distances as lady beetles do."

If you have pests in your garden, the area will attract beneficial insects naturally. Bringing in the insects when the pests aren't there for the predators to feed on won't be much help.