Field Guide to Flies

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DEER FLY/HORSEFLY:

• Similar in shape and appearance to the common house fly, horse flies are larger (approximately 1 1/8″ long for adults).
• Deer flies are ¼” to ½” smaller than horse flies, and usually have patterned wings.
• They may be black, gray or brown in color.
• Larvae proliferate in water or moist soil.
• Winged adults emerge in early summer.
• Adults live only a few days, and eggs are laid on aquatic plants just above water level.
• Powerful fliers that can travel many miles from breeding sites to find meals.
• Female deer and horseflies feed on blood from large mammals (although males do not).

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• Known scientifically as Musca domestica, the most common fly found inside homes.
• About ¼” long and gray with black stripes on the thorax.
• No chewing mouthparts, just “sponging” mouthpart for absorbing fluids, such as tears and wound secretions.
• Breed and produce maggots in moist organic material, such as manure.
• Found year-round, inside and outside, as long as temperatures are warm.
• Does not bite.

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• Resembles the house fly, but with piercing mouthpart to suck blood.
• Both males and females attack animals around the flanks and below the knees, causing them to stomp or kick.
• After feeding, flies retreat to fences or other surfaces to digest their meals.
• Eggs are laid in moist organic matter, such as wet manure or urine-soaked, fermenting straw, hay or feed.
• Life cycle completed in 21-25 days during warm weather.

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• Small, about 3/16″, and dark gray.
• Feed by sucking blood from horses and cattle throughout the day, resting continuously on the animal’s shoulders and back.
• Females lay eggs in fresh cow manure piles.
• Life cycle completed in 10-14 days.