Hover flies — known as sweat bees — annoying but harmless

GREENFIELD — Often, the colors of black and gold found together in nature instill a sense of fear and encourage avoidance both in humans and other species. And when they are accompanied by an endless buzzing and activity that violates our personal space there is often a call to action to remove the “offender.”

One good example of this can be found in the recent appearance of small hovering black and gold colored “sweat bees” that are being reported across central Indiana. They can be found dancing about our landscapes in an annoying (some say “threatening”) manner.

Well, let’s clear the air on this issue.

First, they are likely not bees. They are flies — hover flies or syrphid flies — and while their antics can be annoying, they are entirely harmless and in fact are very beneficial. While there may well be other bees and wasps present with similar coloration, hover flies are true flies so they cannot sting.

Hover flies also have other names such as sweat “bees” or flower flies depending on their habits and habitats and I have recently even heard the referred to as corn flies though I am not sure of any correlation.

Hover flies are much better at hovering than bees and wasps. In fact, they can even fly backwards with ease. With wing beats alone, they effortlessly hang out over flowers until the right moment to descend to feed on flower nectar or pollen.

They are true foodies as they meticulously enjoy each morsel. In dry years, these same insects may land on us to gather a drink of sweat, hence their sweat bee name which does sound better at least than “perspiration bee.”

Insect stings are no fun, and for some people can be life-threatening. There are indeed several Indiana wasps and bees that are capable of stinging. However, since their goals in life are feeding and reproducing, even true bees and wasps prefer not to sting unless threatened.

There are smaller, darker bees called sweat bees that can also hang around us and these can sting if you accidentally squish them.

Yellowjacket wasps also have the characteristic black and yellow coloration and can, and often, do sting.

This time of year they are seeing sweet food sources and I associate them with hanging around trash cans and associated sweet soft drinks, overripe fruit etc.

Yellowjackets don’t hover as well, are more obnoxiously persistent and are larger at one half inch with a more pointed head. Yellowjackets are insects with an attitude. If possible, slowly move away from yellowjackets instead of trying to swat them and only managing to make them mad.

Hover flies don’t deserve the bad reputation so well-earned by similarly colored yellowjackets.

They are significant pollinators and their larvae are essential predators of garden pests. The larvae love a good meal of aphids. Hover fly larva suck out the aphid juices and toss the exoskeleton.

Hover fly larvae are also important predators of pests, such as scales, thrips and caterpillars, and should be protected from insecticidal sprays, even something as seemingly benign as insecticidal soaps.

According to Cornell University each larva can consume 400 aphids before they become an adult fly. That’s 400 aphids that you don’t have to spray to control. When hover fly larvae populations are high, they may control 70 to 100 percent of an aphid population. Aphids alone cause tens of millions of dollars of damage annually to crops worldwide, so the aphid-feeding hover flies are being recognized as potential agents for use in biological control.

If you would like to increase the number of hover flies in your landscape, white or yellow flowers with easy-to-access nectar and pollen such as sweet alyssum, parsley, dill, yarrow, clover and buckwheat are especially attractive to adults and planting these can be a good way to bring them into your home garden.

Rather than being considered harmful, hover flies are a win-win for gardeners since not only are their larvae munching on the bad guys, but the adults are great pollinators.

Let the black and gold color pattern be a reminder of concern only for the insects with stingers and Purdue rival football teams.