The most useful insects in a home garden are the ones that eat or parasitize pests: lady beetles, green lacewings, hover flies, tiny parasitic wasps, ground beetles, assassin bugs, soldier beetles and spiders, plus the bees and flies that pollinate. You usually don’t need to buy them. Most gardens already have them, and the best way to get more is to stop killing them by accident and give them flowers to feed on.
The catch is that many beneficial insects look unfamiliar, especially as larvae, and get sprayed or squashed by mistake. Here’s how to recognize them.
The main groups of garden helpers #
University of California’s IPM program sorts natural enemies of pests into two big groups:
- Predators eat pests outright. Lady beetles, lacewings, syrphid (hover) flies, spiders, assassin bugs, minute pirate bugs, ground beetles, damsel bugs and predatory mites are all on UC’s list.
- Parasitoids are wasps and flies whose larvae develop inside or on a pest and kill it. They include tiny wasps such as Aphidius (aphids), Encarsia (whiteflies) and Trichogramma (moth eggs).
UC IPM calls natural enemies key components of pest management and recommends protecting them by avoiding broad-spectrum pesticides and planting flowers that support them.
Beneficial insects you’ll actually see #
| Insect | What it looks like | What it eats |
|---|---|---|
| Lady beetles (adults) | Round, domed, red, orange or black, often spotted | Aphids, mealybugs, scale, mites |
| Lady beetle larvae | Spiny, black and orange “little alligators” | Same as adults, often more |
| Green lacewing larvae | Flat, tapered, with curved pincer jaws | Aphids and other soft-bodied pests |
| Green lacewing adults | Delicate pale green with lacy, see-through wings | Mostly nectar and pollen (some eat pests) |
| Hover fly larvae | Small, legless, slug-like maggots on aphid colonies | Aphids, thrips and other sap-feeders |
| Hover fly adults | Look like small bees or wasps, hover at flowers | Nectar and pollen; important pollinators |
| Parasitic wasps | Tiny, often under 1/8 inch, rarely noticed | Develop inside aphids, caterpillars, whiteflies |
| Ground beetles | Shiny black or metallic, fast, active at night | Slugs, caterpillars, insect eggs, cutworms |
| Soldier beetles | Soft, elongated, orange or yellow with dark patches | Aphids, insect eggs, and pollen |
| Assassin bugs (including wheel bugs) | Long head, curved beak, often gray or brown | Caterpillars, beetles, other insects |
| Spiders | Many shapes, webs or hunting | A wide range of insects |
Lady beetles #
Adult lady beetles are the best-known garden predators. Their larvae, which look nothing like the adults, eat just as much and are the ones most often killed by gardeners who think they’re pests. If you see spiny, black and orange larvae on a plant covered in aphids, leave them. For telling native species from the Asian lady beetle that invades homes in fall, see Asian lady beetle vs ladybug.
Green lacewings #
Lacewing larvae are sometimes called “aphid lions.” They grab aphids with long curved jaws and suck them dry. The delicate green adults fly at dusk and are drawn to porch lights.
Hover flies (syrphid flies) #
Hover flies are the “bees” that hover in place over flowers and dart sideways. They’re true flies, with one pair of working wings, and can’t sting. Their larvae eat aphids, thrips and other plant-sucking insects, and the adults are considered the second most important group of pollinators after wild bees. We cover how to tell them from bees in bugs that look like bees.
Parasitic wasps #
You’ll rarely see these tiny wasps, but you’ll see their work. An aphid “mummy,” a swollen, tan or bronze aphid with a round exit hole, means a parasitic wasp developed inside. A tomato hornworm covered in small white cocoons has been parasitized by a braconid wasp; leave it on the plant so the next generation can hatch. These wasps don’t sting people.
Ground beetles and soldier beetles #
Ground beetles hunt at night on the soil surface, eating slugs, cutworms and insect eggs. Soldier beetles, such as the goldenrod soldier beetle, are orange-and-black regulars on late-summer flowers, eating pollen and small insects.
Assassin bugs and wheel bugs #
Assassin bugs stab prey with a curved beak. The wheel bug, the largest in North America, has a cog-like crest on its back. The Missouri Department of Conservation notes that it eats many pest species, including Japanese beetles, but can give a very painful bite if mishandled. Brush them off rather than slapping them, and wear gloves when pruning.
Praying mantises #
Mantises are famous garden predators, but they eat whatever they can catch, including bees, butterflies and other beneficial insects. They’re fine to have around, but buying mantis egg cases isn’t a targeted way to control pests.
Pollinators #
Bees, including honey bees, bumble bees, sweat bees and mason bees, pollinate fruit and vegetables. Butterflies, moths, hover flies and some beetles pollinate too. Anything that helps predators also helps pollinators.
How to attract and keep beneficial insects #
- Plant small, open flowers. Many beneficial insects, especially tiny parasitic wasps and hover flies, need nectar and pollen from flowers with short, accessible blooms. Dill, fennel, cilantro, yarrow, sweet alyssum, and native asters and goldenrod are popular choices. UC IPM calls these “insectary plants.”
- Have something in bloom from spring to fall, so food is always available.
- Tolerate some pests. A few aphids early in the season feed the predators that will keep aphids in check later. Spraying the first aphids you see starves the helpers.
- Avoid broad-spectrum insecticides. Products that kill on contact kill predators too, and pests often bounce back faster than their enemies. If you must treat, choose the most targeted option and spot-treat.
- Leave some shelter. Mulch, leaf litter in beds, bunch grasses and undisturbed corners give ground beetles and spiders somewhere to live.
- Provide shallow water, like a dish with pebbles, during dry spells.
Should you buy beneficial insects? #
It can work in greenhouses and enclosed spaces. In an open garden, purchased lady beetles often disperse soon after release. Attracting and protecting local populations usually does more for the money. Your Cooperative Extension office can advise on what works for a specific pest in your area.
Know the pests, too #
Before reaching for a spray, confirm what you’re looking at. Several common garden pests look like helpers, and vice versa:
- Japanese beetles are metallic green and copper and skeletonize leaves. See do Japanese beetle traps work for what actually helps.
- Colorado potato beetles and spotted cucumber beetles are round, spotted and easily mistaken for lady beetles.
- Squash bugs, harlequin bugs and stink bugs pierce and suck fruit and leaves.
Identify before you spray #
A quick photo is the easiest way to avoid killing the wrong insect. Insect Identity knows many common garden helpers, including the seven-spotted and convergent lady beetles, common green lacewing, marmalade hover fly, common drone fly, wheel bug, jagged ambush bug, goldenrod soldier beetle, six-spotted tiger beetle, robber flies, mantises and several bees, as well as garden pests like the Japanese beetle, Colorado potato beetle, spotted cucumber beetle, squash bug, harlequin bug and lily beetle. It gives a best match with a confidence score and four runners-up in about a second, even with no signal in the backyard. Larvae look very different from adults, so if a spiny little “alligator” on your aphids comes back with a low score, compare it with the descriptions above. For other stick-shaped garden visitors, see what bug looks like a stick.
Frequently asked questions #
What is the most beneficial insect for a garden? #
There’s no single winner. Lady beetles and lacewings are the best-known aphid predators, hover flies do double duty as pest eaters and pollinators, and tiny parasitic wasps quietly control many pests. A garden with flowers and few pesticides supports all of them.
What do lady beetle larvae look like? #
They’re elongated, spiny, and usually black or dark gray with orange or yellow markings, often described as looking like tiny alligators. They’re found on plants with aphids and are often mistaken for pests.
Are wasps beneficial in the garden? #
Many are. Tiny parasitic wasps control aphids, whiteflies and caterpillars without ever bothering people. Paper wasps and yellowjackets also hunt caterpillars and other insects, though their nests near doors or play areas can be a stinging risk.
Do beneficial insects bite? #
Most don’t bother people at all. A few predators, such as wheel bugs and other assassin bugs, can bite if handled, so observe rather than pick them up.