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August 19, 2015

Do Not Confuse Hover Flies with Sweat Bees

Timothy Gibb, Department of Entomology, Purdue University

A population explosion of tiny flies often called hover flies seems to be occurring in many areas of Indiana.  These small flies are bright yellow and black in color and are often confused with sweat bees or a yellow jacket wasp. 

Hover flies often swarm around people and even land on them when possible.  Rest assured, however, that these are flies and not bees. There is an old adage; two wings fun; four wings run. 

If you look closely at hover flies you will see that they have only a single pair of wings.  That means that they are in the fly group.  Flies cannot sting.

Bees and wasps have two pairs of wings.  Bees and wasps can sting.  Therefore, even though these are nuisance pests, they can not 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 on trees and other plants.  Because they are beneficial and because they do not directly harm people, no chemical controls are recommended.  As the season progresses, we expect to see hover fly populations decline dramatically.

Look for the following key behavioral and morphological differences  to separate hover flies from sweat bees and yellow jackets. 

1. Hover flies have the ability to ‘hover’ or to remain apparently suspended in mid air.  Wasps and bees do not. 

2. Hover flies do not possess stingers – thus they cannot sting.  Wasps can.  

3. 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.

4. Hover flies are smaller and have fewer yellow lines on the abdomen than yellow jackets.

​Click images to enlarge

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Figure 1
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Figure 2-Sweat bees often have a metallic colored head and thorax.
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Figure 3-Yellow jackets are usually larger than hover flies and have a distinct yellow and black striped abdomen.
 
*Photos courtesy of John Obermyer​