Rochester Sentinel Article

August 29, 2015

Guilt by Association


Guilty, by association. That is the verdict that has been passed down this summer to one of the good guys in the bug world. An insect known as a hover fly, specifically the syrphid fly, has been abundant this summer.  It resembles what most of us think as a sweat bee. These small flies are bright yellow and black in color. Unlike bees, that have four wings, hover flies have the normal fly family characteristic of sporting two wings. They also cannot sting.

For some reason they like to hang around and even land on humans. This elicits a panicked flailing of arms in those people who fear being stung by a “sweat bee.”  All hover flies can do, is just what their name implies, hover. They can remain suspended in midair. Bees cannot do this.

Syrphid flies have a hairless body, and are more brightly colored (yellow and black abdomens) when compared to sweat bees.

Why so many this year? Ma syrphid likes to lay her eggs near aphids. After hatching out, the young larva will move along plant surfaces, lifting their heads to grope for prey, seizing them and sucking them dry and discarding the skins. A single syrphid larva can consume hundreds of aphids in a month.

Aphids, on the other hand are feeding on your plants. Normally soybeans can have substantial aphid populations, this year there appear to be more in corn.  However, we do not think there is enough to cause any problems with corn. 

In general aphid populations build as the summer goes along and hence, their predator numbers also increase right along with them.  As we get to harvest time all these populations will crash, and just become a memory.

Well, sort of. If there is an abundance of aphids, then syphrid flies will not be the only thing eating them.  There may also be a lot of those 19 spotted Asian ladybeetles feeding away.  These beetles like to spend the winter in your nice warm, toasty house. They are a lot more of a nuisance than some bug hovering around you.  These beetles are no ladies, they will pinch.

Mark Kepler

Purdue Cooperative Extension Service-Fulton County

1009 West Third Street                                                                                                                                   

Rochester, IN  46975                  574 223-3397