What You Need to Know About Beneficial Bugs

If you have plants in your garden that attract pollinators, take a closer look at what's landing on those flowers. Chances are they're getting many more visitors than the honeybees, bumblebees and butterflies you're accustomed to observing.

You're likely to see an amazing diversity of smaller insects that you've never noticed before — damsel bugs, lacewings, wasps that look like wasps (and wasps that don't) as well as a variety of flies that look like bees but aren't. Look up, and you might even see a dragonfly hovering overhead. Welcome to the fascinating world of beneficial insects. It's a little-noticed group, but one that brings not only diversity but also gives pollinator gardens an added super power: These good guys eat tiny bad guys, such as mites and aphids.

"Pollinators get a lot of press," Becky Griffin, school and community garden coordinator for the University of Georgia's College of Agriculture, told Treehugger. "But if you're gardening to take care of your pollinators, go ahead and start taking a closer look, because you are going to be attracting all sorts of beneficial insects as well."

Being familiar with a wide variety of pollinators is a specialty for Griffin, who also manages UGA's Pollinator Spaces Project, which encourages gardeners and public landscape managers to leave a dedicated space for pollinators.

Griffin's definition of a pollinator garden is as simple as it is achievable: It's a garden in which the floral resources include a variety of plant and flower sizes that produce a succession of blooms throughout as much of the year as possible. This ecosystem will attract a surprising number and diversity of beneficial insects you won't immediately recognize — simply because you aren't used to looking for them. And even if you have been looking, they are easy to miss; they tend to be smaller than honeybees, bumblebees and butterflies.

To help identify beneficial insects, Griffin recommends contacting your local cooperative extension office. Ask them to send you copies of the information sheets they use rather than referring you to a bigger field guide.

"A field guide for insects would probably be overwhelming because it would include more insects than you want to know about," she said, adding that beneficial insects tend to be localized. "By asking your county extension agent to send you the resources they use, you can create your own field guide," she said. For example, here's one for Southern gardeners: "Beneficial Insects, Spiders and Mites in the Southeast" [PDF] by Kris Braman, Frank Hale and Ayanava Majumdar from UGA, the University of Tennessee and Auburn University.

You also probably already have another handy insect ID tool in your pocket: a smartphone. Because the small size of beneficial insects complicates the difficulty in identifying them, put your camera phone close to the insect and use the magnifying option to enlarge your view. You can take a photo of it, or just use the enlarged view to help you compare the insect with another image.

Here are photos and descriptions of 12 beneficial insects to start your own resource guide to helpful bugs.

Parasitic wasps

Parasitic wasps don't look like wasps. In fact, they're small enough that you may not even see them. You'll see their work, though, in a reduction in pests such as aphids, scale insects and whiteflies. They help control pests by paralyzing them and laying their eggs inside them. To be able to do this, parasitic wasps must be small, usually only an eighth of an inch to a half-inch long.

"I noticed I was getting aphids on my lettuce, but I didn't have time to do much about it," Griffin explains. "Normally, I take a paper towel, dampen it and just wipe them off the lettuce leaves. A couple of days later, I got home and noticed that my aphid population had decreased even though I hadn't done anything. So, I took a lettuce leaf and put it under my microscope and discovered that parasitic wasps had laid their eggs inside an aphid. As those eggs hatched, the larvae ate out the insides of the aphid and emerged as parasitic wasps."

Griffin’s experience illustrates the importance of floral resources in or near the vegetable garden. They attract parasitic wasps and then help to keep their offspring around. "It's a really kind of cool way to regulate your pests a little bit," said Griffin. "If you have very small asters in your garden with flowers that are smaller than a penny, you may get a lot of these," she said. Other plants with small flowers you may want to consider are fennel, chamomile and tansy.

Paper wasps

In a very general way, paper wasps, which are typically reddish brown with yellow markings, resemble the more familiar and aggressive pest wasps. They love to feed on caterpillars and kill them by stinging and paralyzing them. Sometimes you can see one carrying a caterpillar back to its nest.

"People always wonder if a paper wasp is going to sting them," Griffin said. That's not likely, even though they have stingers. "Remember, if they are on the flowers, they are not interested in you unless you do something foolish." Paper wasps are active throughout summer.

Lady beetles

As children, we learned the nursery rhyme, "Ladybug, ladybug fly away home. Your house is on fire and your children are gone." No wonder many adults still call these insects ladybugs. They are not bugs! They are beetles — lady beetles.

By any name, though, these recognizable bugs are popular with gardeners because they feast on aphids, scale insects, mites and mealybugs. Sometimes people buy them in cartons or netted containers and release them in the garden to control these pests. That's an environmentally sound method of insect control. Just remember, though, that once you release them, you have no control over whether they'll stay in your garden or fly elsewhere.

Something else to be aware of: It may not be a good thing if you see an insect resembling a lady beetle on your beans. That's because it may be a Mexican bean beetle, a lady beetle look-alike that feeds on snap and lima beans. "By the same token, Mexican bean beetles are not going to be hanging out on your flowers," said Griffin. So, If you see an oval spotted beetle like the one in the photo above on your flowers, it's probably a lady beetle.

Lacewings

The name "lacewing" does this insect an injustice in its adult stage when its diet is only nectar and pollen. The larval stage is another matter. In this stage, it's known as the "aphid lion" or "aphid wolf" because the green lacewing (Chrysoperla rufilabris) will "wolf down" problem insects, as many as 200 aphids a week by some counts. And if it's still hungry, it will cannibalize other lacewing larvae.

"They are neat, and it's really fun if you can get your camera on them and watch their mouth parts," said Griffin. Adults can be green or brown with their wings showing a distinct network of veins. The larvae are oblong and have soft bodies with distinctive sickle-shaped lower jaws.

Damsel bugs

Many times when you see a plant with a lot of aphids, the first reaction is to hit it with an insecticide or to cut the flowers and stems, put them in a lawn bag with grass clippings and garden debris and set the bag on the curb. Try to resist that urge if you can and go with Plan B, which is to wait for nature to take its course and send beneficial insects such as damsel bugs to solve the problem for you.

Damsel bugs are slender and elongated and may be cream-colored, dark brown or black. They are most active in mid-summer and feed on thrips, aphids, mites and the eggs of many insect pests. If you can hang on and let the damsel bugs bring the population of bad guys into check, then you can leave the flowers alone and wait for them to go to seed in the fall and attract birds. But if the pests become an infestation, you may not be able to wait. That's a judgment you will have to make. Some flowers such as gauria are known for attracting aphids.

Assassin bugs

Assassin bugs are bigger than many other beneficial insects. They are really interesting, but you shouldn't pick them up because they can inflict a painful bite, Griffin said. So how big are they? "Not quite as big as a praying mantis, but about as big as your index finger." How painful is their bite? "It won't put you in the hospital, but you will know you have been bitten," she said, adding that she likes to watch them from a safe distance. They move slowly, like a chameleon, and are generally oval-shaped or elongated with a head that's noticeably long and narrow. They are usually black, orange-red or brown. They are predatory insects that feed on a wide variety of insects, ambushing their prey, piercing the victim's body with a short three-segmented beak and then sucking out body fluids.

Two-spined soldier bugs

The two-spined soldier bug is the most common stink bug in North America. It gets its name from having a spine that comes off each shoulder. In the adult stage, its body is light brown and shield-shaped. It's beneficial in the garden because it preys on more than 100 pest species, primarily caterpillars and beetle larvae. Gardeners should be aware that a mature squash bug — which is a garden pest — resembles the two-spined soldier bug. "If you see a bug that looks like the two-spined soldier bug on your squash or pumpkins, the chances are that it's a squash bug and not a good bug," said Griffin. Squash bugs suck the sap out of plants.

Garden spiders

Spiders are generalists when it comes to prey and will eat the bad guys as well as the good guys in your garden, says Griffin. "Spiders can be pretty much lumped together because they will spin a web and whatever gets caught in the web is what they will go for."

You can often find garden spiders in the flowers you plant to attract beneficial insects in and around the vegetable garden. "I am trying to attract butterflies and bees, and I don't want spiders eating those things." When a spider shows up in an area where Griffin doesn't want it, she has a handy way of solving the problem. "I found a really big riding spider in my cosmos plants, and I just got a big broom and put her on there and moved her to the other side of the garden where I knew there were some beetles she could trap. That kept her out of my bumble bee area!"

Praying mantis

You don't see them that often, but praying mantises are fun to watch when you do. They get their name from the way their front legs are folded into a position that looks like a person praying. These front legs have sharp spines that hold their prey, which include insects such as crickets and grasshoppers that harm crops as well as spiders, lizards, frogs and even small birds. They can sometimes be difficult to see because their colors and the shape of their body help them blend in with plants. "Whenever I find them, I always move them close in to where I want predators," said Griffin. Their egg sacs, which can become a hardened mass on twigs or stems, can be another indicator of their presence.

Dragonflies

Dragonflies were here before the dinosaurs roamed. Even thought they've been around for a long while, we underestimate them. "This is a beneficial insect that people don't think about very often," Griffin said. Unless you have a pond. Then you may think about them more often because there's an aquatic aspect to dragonflies — the females lay eggs on the water's surface or sometimes insert them into aquatic plants or mosses. If you have a pond, it's good to have dragonflies around because dragonfly larvae will eat mosquito larvae and help keep mosquito populations under control.

Adult dragonflies have four sets of wings and an ability to operate each wing independently. That makes them excellent fliers, which is important because they catch all their prey with their legs while in flight. Their diet consists of numerous insects, including pests, such as mosquitoes and midges as well as butterflies, moths and even smaller dragonflies.

Syrphid flies

Syrphid flies are also known as hoverflies. They get that name from their ability to hover like tiny helicopters in your garden and from the ability to fly backwards, something highly unusual in the insect world. In the larval stage, they feed on pests such as aphids, scale, thrips and caterpillars. As adults, they help control aphids and act as pollinators on flowers as they hover over them. Many species look like bees. The best way to distinguish between a bee and a hoverfly in your garden is to look at the face. Flies have large eyes that cover most of the head. You can also look at the wings — if they'll hold still long enough! Flies have two wings, while wasps and bees have four.

Robber flies

A robber fly is a medium-to-large, stoutly built fly that's sometimes called an assassin fly. This is an aggressive predator that will attack yellow jackets and hornets, the kinds of things other insects avoid. Because of that, they are considered a beneficial insect. However, they are not choosy and will attack pollinators, such as bees, even if the bee is larger than they are. They catch their prey by ambushing them in mid-air, kill their victims by paralyzing them and then eat them by sucking out their insides. A defining characteristic of these unique-looking, hump-backed insects is a distinctive hollow space between their large compound eyes.

When you see them zooming around your garden, the tendency is to think, "Oh my! Somebody's on the prowl," said Griffin. Their flight patterns, she added, make her think of Wagner's "Ride of the Valkyries." "The robber fly is a really unique thing to look out for," Griffin said. "They are very serious flyers, and when they show up, they are there to do business!"