Frustrations of Fly Season

Bugs that bite certainly get our attention. If you have ever been bitten by a horse fly or a deer fly, you can relate. Not to mention the mounted challenges that can come when one of these nasty critters are after our horse.  Keeping ourselves and our horse focused during a ride can be challenging enough without these pesky distractions! 

The biggest attackers, the horse fly, may reach an inch in length. There are about 350 species in North America. The name horse fly refers to its attraction to horses and other large animals, including people. A horse fly’s body is mostly hairless and often black, gray, or brown with a broad band on its large abdomen. The fly has short antennae and large, iridescent green and purple eyes. The male horse fly stays among plants and feeds on nectar and pollen. The female, on the other hand, searches for a meal of blood. Her bladelike mouthparts cut skin. She usually goes for legs or wet, sweaty skin, so easy to find in the summertime.  And the summer has just begun! This is one of many good reasons to provide plenty of shade for our animals in the summertime. The greatest horse fly activity occurs on warm, sunny days when there is little or no wind. A slight drop in temperature or a sudden breeze reduces biting attacks. Horse and deer flies are visual insects, locating hosts by movement. Dark, moving objects and shapes are most attractive to the flies.

Close cousins of horse flies are deer flies.  The name deer fly refers to its habit of feeding on white-tailed deer. Deer flies are those pesky bugs that buzz around our head on hot summer days. The deer flies lie in wait in shady areas under bushes and trees for a host. Sight is the main host finding mechanism, but carbon dioxide and odor also play a role.  Attacks occur during daylight hours with a peak beginning at sunrise and lasting three hours. A second peak is two hours before sunset and commences shortly after. Attack frequency is low on overcast days or at cooler temperatures. One good thing is that horse flies and deer flies retire for the night, and they are not around for long; mostly in July and August. 

Fly sprays are all but ineffective when it comes to horse flies and deer flies. The best control is obtained by trapping the female flies before they have the opportunity to bite or reproduce. A number of fly traps have been developed which attract these flies using dark, moving objects, as well as carbon dioxide and other attractants. Although these traps will not completely eliminate all the flies, they will reduce the populations to a more tolerable level. Minimizing outdoor activity when flies or more active during dawn and dusk hours may be a solution.  Allowing horses to come inside a barn during the day, if possible,  may be another alternative to consider. 

Summertime has many advantages; the warm, long days, flowers blooming, fresh produce, and green pastures.  Learning to deal with flies and other insects is just part of it.  Enjoy your summer, and best wishes with learning ways to avoid these nuisances! 

Original article written by Will Walls, Johnston County REINS volunteer, 2010.  Modified by Eileen Coite, County Extension Director, Sampson County Cooperative Extension.