With their black-and-yellow coloring and striped abdomen, hoverflies might look like bees or wasps at first sight but because they are flies, they don’t sting. Not only are hoverflies harmless, they are highly beneficial insects whose larvae provide natural insect control by feeding on aphids and other small insects. Adult hoverflies also play a significant role in crop pollination.
Therefore, it’s a good thing when you see hoverflies in your yard. If you haven’t spotted any, there are ways to attract them with their favorite flowering plants.
What Are Hoverflies?
Hoverflies, also called flower flies or syrphid flies, are insects of the order Diptera and thus, true flies. They make up the insect family Syrphidae, which consists of 200 genera and 6,000 species, ranging in size from less than one-quarter of an inch to more than three-quarters of an inch in length.
The name hoverfly comes from the ability of the adults to hover over flowers like a helicopter. They can also fly backwards, an ability rarely found among other insects.
Their resemblance with bees and wasps such as yellowjackets serves them well in the insect world—it protects them from predators.
How to Identify Hoverflies
Many hoverfly species have black and yellow stripes on the abdomen. This makes them look like bees or wasps but there are several significant differences.
The major difference is also the easiest to remember: it’s the old saying, “two wings fun, four wings run.” Flies only have one pair of wings, whereas bees and wasps such as yellow jackets have two pairs of wings.
If you don’t feel comfortable getting close enough to see the number of wings, you can identify hoverflies by their ability to hover in mid-air over a flower in search of nectar, a skill that bees and wasps don’t have.
Another behavioral indicator that can give away the hoverfly is their presence near aphid populations where they have laid their eggs. Typically, you’ll see hoverflies later in the growing season when aphid infestations are at their peak.
A behavior that hoverflies share with sweat bees is that, attracted by human sweat, they tend to hover around the face and other exposed body parts arms (remember, hoverflies do not have a stinger so they cannot harm you). The metallic greenish color of most sweat bees is different from hoverflies, which makes it easy to tell them apart.
Habitat and Life Cycle of Hoverflies
The American hoverfly Eupeodes americanus (Metasyrphus americanus) is found throughout North America, but there are numerous other hoverfly species that are only found in certain regions and are well-adapted to a specific habitat.
Common to all hoverfly species is that the females repeatedly lay their tiny single white eggs, which look like miniature grains of rice, on leaves or green shoots in the vicinity of aphid colonies. The larvae hatch in two to three days. With their legless bodies, they resemble maggots. The larvae then move around the undersides of the leaves on the plant seeking out food, aphids being their favorite meal. During the two to three weeks until the larvae reach their next development stage and pupate, a single larva devours up to 400 aphids.
Adult hoverflies need flowers to feed on nectar, preferably near plants with aphid infestations where they will lay their eggs, thus continuing the life cycle.
There can be five to seven generations of hoverflies per year. The number depends greatly on the climate, the species, and how much food is available.
Garden Benefits of Hoverflies
Because hoverfly larvae are such voracious eaters, a healthy population of hoverflies can reduce aphid populations by 70 to 100%. Hoverfly larvae feed on aphids that suck the sap out of shoots and leaves of citrus and other subtropical fruit trees, grains, corn, grapes, vegetables, and ornamentals.
Aphids are not the only pest that hoverfly larvae can help control. They also eat small caterpillars such as cabbageworms, thrips, scale insects, mites, and other small insects.
As the adult hoverflies move between flowers in search of nectar, they perform the important task of pollination by carrying pollen from one plant to another.
How to Attract Hoverflies
Even if you are in the lucky position of not battling any aphids, attract hoverflies to your yard because they are important pollinators. Flowers they prefer include Queen Anne’s lace, sweet alyssum, cosmos, zinnias, daisies, and other small, flat flowers that give them easy access to nectar. They also like herbs with small flowers. Lavender is usually the only herb that is not cut for consumption and gardeners allow to reach the flowering stage. To provide nectar for hoverflies, don’t cut all of your herbs such as cilantro, dill, chives, thyme, mint, and parsley flower, and let them flower.
Syrphid Flies (Hover Flies, Flower Flies) Washington State University.
“Syrphid Flies (Flower/Hover Flies) University of Maine Cooperative Extension.”