One likes dark shapes; the other favors shiny objects, CO2 Horse- & deer-fly invasions

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Deer-fly

By Eric Barrett

OSU Ext. educator

Some areas of the Mahoning Valley have experienced heavy populations of horseflies and deerflies this summer.

The sometimes tremendous size of horseflies can be quite scary. This is because the thought of getting bitten by something that big makes your skin crawl. These flies are good at sneaking up on you and biting you before you know it. Deerflies are smaller than horseflies, but still larger than house flies.

Horsefly and deerfly larvae live in ponds, streams and marshy areas where they feed as predators of other insects for one to several years, depending on the species. Thus, they can be anywhere — in the city or in the country. When the flies are ready to pupate, they move from the water to start their next phase of life as an adult fly.

Our OSU Extension fact sheet on the subject (see link below) states that female horseflies require blood meals to be able to produce eggs to initiate the next generation, thus they search for large mammals — people or animals — from which to obtain their blood. When the prey is located, the female uses her sharp mandibles to slash a wound in the skin and laps up the blood. The bite is generally extremely painful.

Horseflies are adept at locating warm-blooded animals, including people around woodland areas with streams. This is a reason to take precautions before enjoying the outdoors this time of year.

Our entomologists say these insects are most active on sunny days with little wind. They are less active on the cooler days. Dark shapes and moving objects are the big attractants for deerflies, thus light-colored clothing is recommended when going on a hike or enjoying park areas. Horseflies are slightly different in that they are attracted to motion, shiny objects and carbon dioxide.

Stay alert while outside working — because unlike most other flies, deerflies and horseflies don’t buzz very much and can sneak up on you.

Try to avoid perfume, scented hair products and creams when spending time outdoors. A good option is to use an insect repellent containing DEET to prevent them from even thinking about you as a meal. Remember to read and follow all label directions before purchasing and using any chemical product.

Many homeowners have asked about reducing populations near their homes this summer. Unfortunately, there are no good control options. Using a spray will knock down the existing flies in the area, but more will come later in the day or on the next.

For more information on horse and deer flies, go to: http://go.osu.edu/horsedeer.