GARDENING : FAR FROM BUGGING YOU, SOME INSECTS ARE HELPFUL.

Byline: Joshua Siskin

If misunderstanding is the source of fear, long-dreaded garden pests will be regarded with affection after reading ``Dead Snails Leave No Trails'' (Ten Speed Press; $11.95). Loren Nancarrow and Janet Taylor, the authors of this concise volume, offer a great service in demystifying the pestiferous critters - from insects to reptiles to rodents - in whose midst we make our homes.

Let's say that all your life you have had nothing but loathing for ants. Now hear this: ``Ants are great soil mixers. Ants turn over tons of dirt building their nests, and often are called the `composters' of the insect world. Ants are scrupulously clean. They have a comb on the middle joint of each front leg they use to clean their bodies. Some birds will actually allow ants to crawl on their bodies to clean them of unwanted parasites.''

If you still are uncertain about welcoming ants into your garden, a recipe for their demise is presented: 1 tablespoon boric acid powder, 1 tablespoon sugar and -1/3 cup water. Mix these ingredients together and then divide between two small jar lids or cut down paper cups. Indoors, any household cleaner containing ammonia or pure citrus extract is effective at stopping ant invasions.

Those large green buzzing metallic beetles - known as fig, fruit or June beetles - have become quite a nuisance in recent years. In compost piles and mulched beds they lay their eggs, from which large, white grubs emerge. The grubs eat the roots of ornamental plants while the adults gorge themselves on figs, peaches, grapes, apples, melons and tomatoes. To stop fig beetle proliferation, stretch and secure clear plastic sheets over ground where grubs are discovered. When adults emerge, they can be easily spotted, picked up and disposed of - after plastic is rolled back - before they are able to fly off and mate. Still, ``many people who have compost piles actually find the beetle grubs to be very beneficial. The grubs aerate the pile and move a lot of decaying material through their bodies, turning it into usable compost.''

The cucumber beetle is an attractive relative of the ladybug, only its black-spotted wings are yellow or green, instead of orange or red in color. Unlike the beneficial ladybug, the cucumber beetle is a pest of cucumbers, squash, melons, beans, peas, corn, beets and tomatoes. It will also suck on tree fruit and take bites out of flowers such as daisies and cosmos. A preparation called cucumber beetle death repellent is recommended. It is formulated on the principle that beetles are repelled by the smell of their own dead. ``Kill 50 beetles by placing them in a jar with a cotton ball soaked in fingernail polish remover. Put the dead beetles in a blender with two cups of water and puree. Spray or drop the mixture around the plants in your garden.''

The book devotes one chapter to beneficial insects and animals. Bats receive top billing for their control of mosquitoes, gnats and just about every other kind of insect. A plan for a small bat house is included. A side benefit of creating a bat shelter is guano - long recognized as a superior fertilizer.

Beetles are the largest group of insects. The number of beetle species, which is more than 250,000, is roughly equivalent to the number of plant species that have been identified. Many beetles are beneficial, but those that may do the most good keep a low profile, as they dwell in the earth and are known as ground beetles. Ground beetles have shiny exteriors, usually black in color, but occasionally green, red or blue. Experienced gardeners are familiar with these beetles, which run away quickly, but seldom fly, when they are disturbed. Ground beetles consume cutworms, grubs and root maggots, as well as snails and slugs.

Hover or syrphid flies, those tiny motionless ``helicopters'' around your flowers, are avid aphid and mealybug eaters. Female hover flies lay their eggs right in the middle of an aphid colony. The emerging larvae feast on the surrounding aphids by grabbing onto them and sucking the fluid out of their bodies.

The common honeybee arrived in this continent in the 17th century, along with the colonists from Europe. It was brought over for the purpose of making honey and wax. Only in this century was its importance to agriculture appreciated. Forty-two of the crops grown in California - including almonds, alfalfa and avocados - could not be grown without this European bee.

Praying mantises, by the way, are not at the top of the list of carnivorous insects. The problem is that they do not discriminate in their diet between beneficial insects and insect pests, and will even feed on one another.

Tip of the week: Garlic is recommended as a repellent to aphids when planted around fall and winter vegetables, such as cabbage, cauliflower and Brussels sprouts. Garlic planted next to roses is supposed to prevent the occurrence of black spot. Garlic tea, sprayed on plants, is said to protect against insect pests and mildew. To make garlic tea, steep 1 chopped garlic bulb (about 20 cloves) in 1 quart of hot water for 24 hours. Strain and spray.

MEMO: Joshua Siskin's column appears every Saturday. He welcomes questions from readers. Write to him in care of the Daily News Features Department, P.O. Box 4200, Woodland Hills, Calif. 91365-4200. You can also reach him through this on-line mailbox: JoshSiskinaol.com.