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What Just Bit Me? Biting Flies Explained

R. Bessin, University of Kentucky

You're going for a walk through your neighborhood and suddenly a large horse fly starts buzzing aggressively around your head. Or maybe you're sitting at a picnic table and you have to keep shifting your legs because a little deer fly bites at your ankle. UK Research and Education Center at Princeton's entomologist Dr. Doug Johnson briefs us on the family Tabanidae, or biting flies, on Sounds Good.

Tabanidae is the family name for horse flies and deer flies, known for their painful bites. Most of the flies in this family are at least as large as house flies (Tachinidae), but can be distinguished by their unusual antennae (three segments), one pair of wings and mouths built for biting and sucking. The Tabanidae family is quite large, with over 3,000 species, but the most common in Kentucky are the horse fly and deer fly. 

Aggressive Horse Flies

Typically between 1/2 to 3/4 inch, horse flies are robust, stout and very fast. They have large compound eyes often brightly colored. They resemble house flies in body shape, but are generally much larger. While they may seem territorial, Dr. Doug Johnson says you cannot asses territoriality with these creatures in the same way you would a dog or coyote. 

Horse flies have a predatory range of several miles, but may stay in a particular area in which they do well. Usually these places have an aquatic element (a bucket of water, damp spot in the woods) where they can raise their larvae successfully. Dr. Johnson says they need to have a blood meal to nourish their eggs to generate offspring, so if they tend to be in a particular area, they are in a place that is successful for them.

Smaller Deer Flies

Like the horse fly, these flies will bite and will do whatever it takes to get the meal they require. You may notice them around your ankles and extremities. Dr. Johnson says these are tenacious creatures that are particularly good at identifying heat and chemical signatures that will provide them a nourishing meal for their offspring.

Dr. Doug Johnson

Important to the Ecosystem?

Flies are a source for food for birds and smaller animals. Predatory flies may eat other things humans may prefer not to have around. Dr. Johnson reminds us that insects aren't around because they're "good," they are around because they are successful at what they do. They are not human and aren't thinking about contributing to the environment. They live and reproduce.

"Just remember that there are basically more insect species than all other animals on Earth combined. So if you want to have that philosophical discussion on what is successful and what is not, that'd be a good place to start."

More about Tabanidae at the UK Entomology website

Matt Markgraf joined the WKMS team as a student in January 2007. He's served in a variety of roles over the years: as News Director March 2016-September 2019 and previously as the New Media & Promotions Coordinator beginning in 2011. Prior to that, he was a graduate and undergraduate assistant. He is currently the host of the international music show Imported on Sunday nights at 10 p.m.
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