Hoverfly larvae are small, tapered maggots that crawl over foliage and help kill insect pests. Black-and-yellow-striped adults resemble yellow jackets but are harmless to humans.
Illustration By Keith Ward
This article is part of our Organic Pest Control Series, which includes articles on attracting beneficial insects, controlling specific garden pests, and using organic pesticides.
Hoverfly or Syrphid Fly (Diptera)
Hoverfly identification is easy if you know what to look for. Black-and-yellow-striped adult hoverflies (also called syrphid flies) resemble little yellow jackets, but they have only two wings and big compound eyes. Size varies with species, with most hoverflies maturing to less than 5/8 inch long, with yellowish markings that help them resemble wasps (thus deterring predation). Attracted by gases given off by warm, sweaty bodies, hoverflies occasionally land on people to lick salty sweat. Be gentle blowing them off, because hoverflies can neither bite nor sting, and are major beneficials in the garden.
Hoverfly larvae are aphid-eating machines, though they are so small you will need a magnifying glass to see them. Adult hoverflies lay scattered eggs on leaves being fed upon by small, soft-bodied insects such as aphids. Upon hatching, the hoverfly larvae scour the leaf surface for food. After a few weeks of feeding, the hoverfly larvae pupate into adults. In warm climates several generations are common.
What Do Hoverflies Eat?
Hoverfly larvae eat aphids, small caterpillars including cabbage worms, as well as thrips, scale, and tiny mites. Adult hoverflies feed primarily on flower nectar, and help pollinate some crops.
Attract Hoverflies for Organic Aphid Control
The hovering behavior of syrphid flies requires a lot of energy, so adults won’t waste time flying about when they can find what they need in your garden. Many annual flowers attract hoverflies, including sweet alyssum and bachelor buttons. Syrphid flies also like the little blooms of buckwheat and most herbs, especially catnip, oregano and late-blooming garlic chives. Tolerate small aphid outbreaks on crop plants when you see plenty of hoverflies in your garden late in the morning, their most active time of day. Especially in summer, hoverflies can provide excellent control of aphids, scale and other soft-bodied insects.
More information about hoverflies is available from Texas A & M University, Washington State University, and the University of Florida.