Background on the Deer Fly and Horse Fly

Tabanidae include both Deer Flies and Horse Flies. Deer Flies are smaller than Horse Flies (1/2” long). Their wings are tinted smoky brown or have dark patterns. Their thorax is greenish-yellow with dark stripes. The eyes touch each other on the top of the head in males and are separated in the females.

Horse Flies are like Deer Flies but much larger and heavier-bodied (1/2”-3/4” long). Their wings are clear and their thorax is usually brownish-grey striped. The abdomen may be orange and black patterned or similar to the coloration of the thorax.

Deer Flies are strong fliers going many miles. They are painful blood feeders and frequently become serious pests of livestock and humans. They are also known as “cedar flies” in parts of the United States. The males are found on flowers and feed on nectar and pollen. The females may be seen circling your head.

The larvae of Deer and Horse Flies are semi-aquatic and are mostly found in moist soil along the edges of ponds, dug-outs and cattail areas of some ditches.

Quick Tips Deer and Horse Flies

• Semi aquatic breeders
• Can fly in from great distances
• Use specialized Horse/Deer Fly traps to reduce populations
• Best remedy is avoidance if possible
• Spray insect repellents on animals away from where Beneficials will be
• No commercially available Beneficials, including Fly Predators, have an impact on these species

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The Horse Fly, like the Deer Fly, is extremely difficult to control. They cause intense pain at the site of the bite, which is very annoying to livestock as well as to people. Unlike the Horse Fly which lumbers around you before biting, Deer Flies zoom in, circle fast and bite quickly.

If repellents or insecticides are used, some decrease in feeding may occur but many will still feed.

Avoidance of heavy feeding areas may be the best preventive strategy for this pest. Fly Predators, House Fly traps and baits have no impact on these pests. An effective trap is the Horse Pal trap (www.horsepal.info) that is specially designed to attract these species plus Yellow Flies and Greenheads. Best placed close to the source of these pests as it can be ineffective when used near areas with many animals (with real blood) as these biting flies are not that dumb.