If picnic reports and phone calls are any indication, we are seeing another late-season population explosion of tiny flies often called hover (or syrphid) flies. August is the time!
These small flies are bright yellow and black in color and are often confused with sweat bees or wasps. If you find yourself harassed by these insects, know that the invasion is seasonal and temporary and that they do an important job in the landscape.
Purdue entomologist Tim Gibb has an expression: “Two wings, fun; four wings, run.” This refers to the fact that hover flies have only a single pair of wings, unlike wasps. Bees and wasps, which certainly can sting, possess two pairs of wings. Even though hover flies can be a nuisance, they cannot sting or harm people.
Hover flies are beneficial because they help pollinate plants and, in their immature stage, they eat aphids that can be pests in the landscape. Because they are beneficial and because they do not directly harm people, no chemical controls are recommended. As the season advances, we typically see hover fly populations decline.
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Gibb suggests looking for these differences to distinguish between hover flies and bees/wasps:
Hover flies have the ability to “hover” or to remain apparently suspended in midair. Wasps and bees can’t do this.
Hover flies do not possess stingers but wasps and bees do.
Hover flies have only a single pair of wings, a hairless body and are more brightly colored (yellow and black abdomens) when compared to sweat bees.
Hover flies are smaller and have fewer yellow lines on the abdomen than yellow jackets.
It’s understandable that anything that shares even some resemblance with the dreaded wasps can be unnerving, especially if one reacts to stings. But it’s good to know that the outbreak is temporary, and that these little guys can really put the hurt on some aphids.