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Most of our garden insects are anything but pests

Late last night I arrived home in the dark – the porch light left off again – and stood still in the driveway, filled with wonderment.

In the meadow just past the mowed lawn a splendid show was in progress: The dance of the fireflies. I tried to count the flashes in my field of vision in one second, between blinks of an eye – 25 here, 50 there. Then I thought about what else lived there, among the tall grasses and goldenrod, asters and brown-eyed Susans, all the creatures that don't flash but complete the business of living just out of human sight. I'm glad it's a meadow, not more lawn.

Insects are generally not popular with humans, but fireflies (also called lightning bugs) fascinate, spark the imagination and often evoke nostalgia – memories of summer nights on the back porch or by the campfire. Even the unromantic among us can appreciate the science: This family of beetles (not bugs, not flies) includes 20 North American genera divided into about 200 species, differentiated by their light flashing patterns. The light is a chemical reaction induced by an enzyme. Their larvae (aka "glow worms"), all have light-bearing cells, but only some species are luminescent as adults. Those we see flashing after sunset are usually males, blinking for the attention of females, awaiting them in the grasses.

It's not all flash-dancing though; the larvae live in the soil and prey on snails, slugs, earthworms, insect eggs, dead insects or decaying fruit. They're helpful little glow worms.

>Each has a purpose

Most people have preferences about what animals are acceptable. Those who care about the plight of elephants and pandas, or invest in habitat protection, might say they "hate flies" or "spiders creep me out." Some spray their lawns or roses "just in case," to kill the bugs.

But if we really care about the ecosystem, we should simply take care of the insects. Keep the streams, fields and forests suitable for caddis flies, lacewings, orchard bees and luna moths, and we'll have healthy frogs, birds and the rest. Without insects, the planet collapses – no pollination, dung removal, pest management or fish food.

In his "Field Guide to Insects of North America" (Hillstar Editions) – by far the best field guide ever – Kenn Kaufman quotes a study by Cornell University and the Xerces Society that attempted to assess the economic value of wild insect services (including related arthropods). All that pollinating, consuming dead things, eating up caterpillars and other creatures, and feeding other animal families would be worth $57 billion a year in just the United States if we had to replace those functions.

Even gardeners, who respect pollinators and protect lady beetles, spiders and other known "beneficial insects," tend to prejudge insects. Even within a garden, a so-called pest (such as aphids) is also food for some insects (lady beetles) or a source of honeydew for others (wasps); those insects then move on to prey on other insects or pollinate plants or feed a bird. In a healthy, diverse system, nothing is a pest. Only when we impose our particular requirements – as in wanting a cutting garden or potato crop – do some insects become pests. We set up monocultures; we have large pest infestations. We put plants under stress; insects attack them. We create the conditions that create pests.

>The armyworms are coming!

Obviously, when growing our food and flowers, some insects are serious foes. They damage plants and interfere with crop production or aesthetic goals. Armyworms, so named because they devastate whole fields, have recently wiped out some Western New York farmlands and crops. It's serious business, requiring appropriate action such as an IPM (Integrated Pest Management) program that involves interrupting the insects' life cycle, and correct product selection and use.

Often the worst foes or pests are non-native insects introduced to an area where they have no natural enemies. The Viburnum Leaf Beetle, Japanese Beetle, Elm Leaf Beetle, Asparagus Beetle, Emerald Ash Borer and Asian Longhorned Beetle all came from elsewhere, on plants carried by gardeners or in crates or packing materials.

Indigenous insects are generally easiest to manage, largely because natural forces collaborate with our efforts: We hose off aphids a few times and Spined Soldier Bugs show up to eat the rest; we till the garden and birds consume insect larvae that were buried all winter. Most leaf-eating insects, including caterpillars, leave holes but move on – to other plants or into other phases of the life cycle – and do no permanent harm to your plants.

So, how can you tell which insects are serious problems that need managing, and which are among the myriads just passing through?

The first answer is: Patrol the garden, watch and learn – a lifetime project. Understand that there are perhaps 90,000 insect species in North America, 24,000 of them beetles. (One-fourth of the animals on Earth are beetles.) We will never learn to identify most of them on sight, but it is possible to see patterns and classify them correctly (beetles, bugs, flies, bees and wasps, moths, etc), which provides a lot of useful information. Most of the insects you see are not pests at all, and even the so-called pests are mostly manageable by common-sense methods (hand-picking, hosing) and by keeping plants healthy.

The second answer, when you know you have a pest problem, is to get science-based help. Look for agricultural college websites, call the Cooperative Extension – and never just spray a pesticide without full knowledge of the pest, the product and the consequences. Many home garden products are used incorrectly and excessively, accomplishing little good and often harming many valuable species.

Insects are mostly wonderful, sometimes a nightmare and always amazing.

Sally Cunningham is a garden writer, lecturer and consultant.