Beneficial Bugs

By Chandra Orr

February 20, 2009 6 min read


Those creepy crawlies can provide protection

Chandra Orr

Creators News Service

That beetle sneaking through the strawberry patch or the wasp divebombing your begonias may send you screaming for the hills, but think twice before you stomp, smash or spray. Looks can be deceiving.

"Although insects are creepy and crawly, many are beneficial, even crucial for a beautiful garden," said Jim Louderman, collections assistant for the Division of Insects at The Field Museum in Chicago.

Lacewing larvae, for example, prey upon aphids, scales and other insects that suck vital fluids from the leaves and stems of plants. They are so potent a predator that garden suppliers sell their eggs by the thousands as a means of inexpensive, eco-friendly pest control.

With their spiny, segmented bodies and long pincers, the larvae may look a bit prehistoric, but they get the job done. Once they emerge, they feed on mealybugs, spider mites, leafhopper nymphs, moth eggs, thirps and whiteflies for several weeks before becoming adults.

The adults, known for their long, membranous wings, eat only honey, pollen and nectar, which they need to mate and produce more pest-munching larvae. A batch of 1,000 lacewing eggs costs about $8 from a garden supplier such as Arbico Organics ( Not bad for natural, renewable pest control.

But lacewings aren't the only beneficial bugs in the garden. Those dangerous-looking dragonflies buzzing overhead adore mosquitoes. The centipedes slithering through the soil snack on slugs and fly pupae. And stinkbugs -- reviled for their pungent odor -- seek out caterpillars and moths.

Help Mother Nature do her thing and think twice before exterminating some of her most powerful predators.


In northern climates, phorid flies -- commonly called humpback flies -- are seen as a nuisance, but in the South, you'd be wise to leave them be. Resembling fruit flies, these tiny terrors excel at eliminating fire ants.

"Phorid flies buzz above the heads of ants and flick an egg on the ant's neck. The egg hatches, and the fly larva proceeds to eat into the neck. The neck gets so eaten up that the ant's head simply falls off," explained entomologist Bob Belmont of Massey Services, one of the nation's largest pest management companies.

It's a bit gruesome, but this natural pest control is a booming success.

"Phorid fly populations continue to strengthen in fire ant-infested areas, and entomologists are working to bring even more species from abroad to further enhance fire ant control," Belmont said.


They may be an annoyance, building paper-thin nests under the eaves and buzzing about on warm summer days, but wasps are one of nature's great pest-control agents.

"Any discussion of beneficial insects has to include the various species of wasps that most people spray into oblivion," said Paul Riddell, owner of the Texas Triffid Ranch, a carnivorous and prehistoric plant nursery in Dallas. "It takes a lot of effort to get most wasps angry enough to sting, and benefits of their controlling the population of caterpillars and cicadas outweigh the risk. Some are nearly microscopic and prey on aphids and mealybugs. Others are the size of hummingbirds and snag grasshoppers and cockroaches."

While many wasps feed on unwanted invertebrates like caterpillars, ants and venomous spiders, others destroy pest populations by parasitism.

"Certain wasps fly up to and land on caterpillars, insert their eggs into or onto the caterpillar's skin and fly away," Belmont explained. "These eggs soon hatch into larvae that immediately begin to feed on the caterpillar."


Praying mantises, also known as mantids, are voracious predators with an appetite for flies, mosquitoes, caterpillars and grasshoppers.

"The praying mantis is related to the grasshopper, but unlike grasshoppers that might chew on succulent garden plants, the mantid is one of the garden's best friends. It eats only other insects -- including many that attack the plants in your garden," Belmont said.

Young mantids snack on leafhoppers, aphids and mosquitoes before moving onto larger prey like beetles, moths and crickets.


They're perhaps the most reviled of all garden creatures, but for all the work they do, spiders should be revered. These potent prowlers feed on a variety of insects that do harm to plants and people.

"There are many insects such as mosquitoes, biting flies, bed bugs and fleas that bite humans and are vectors for West Nile virus, Dengue Fever and malaria. These insects are the primary food for many spiders," Louderman explained.

Don't let their intimidating looks deceive you. Except for black widows and brown recluses, it's safe to let spiders shack up in the garden.

"Spiders rarely bite humans," Louderman said. "Spiders can sense that a human is far too large to be a meal. By biting a human, a spider would waste its venom."

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