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Horse flies and Deer Flies

(Family Tabanidae) All pictures courtesy of R. Grantham, OSU Department of Entomology and Plant Pathology  
A fly with a light green/brown body and dark stripes. Tabanus mularis
A fly with a grey body and dark stripes. Tabanus sulcifrons
A fly with a yellow body and dark stripes on its body and wings. Deer Fly


A fly (circled in red) on the side of a large black cow that is bleeding in sections of its hide.

Tabanids are a diverse group of flies including both horse and deer flies. Tabanids can be one inch and longer in size. Tabanids feed on the blood. Female Tabanids have a painful bite; the males do not feed on blood. Populations will peak from June to September.


Life cycle

Most Tabanids will lay their eggs around edges of ponds in moist mud, making chemical control of larval stages impossible. Tabanids have complete metamorphosis (egg, larvae, pupae, and adult) but generally will only produce one generation per year.  Tabanids have a large flight range and will continually emerge throughout the summer months. This can mean that there could still be Tabanids on the animals after treating the population, through newly emerged adults and incoming flies. These large flies prefer to feed on the backs and legs of animals.

Pictures courtesy of R. Grantham, OSU Department of Entomology and Plant Pathology
An infographic of the life-cycle stages of a horse fly.
An infographic of the life-cycle stages of a deer fly.


Control Methods

Some Tabanids are repelled by sprays but, many of these are not long lasting and are not a practical means of protection. Traps can be used to control Tabanids in a small area but, the number to be effective and cost of traps limits its feasibility.



Tabanids have been shown to be carriers of Anaplasmosis and Tularemia and can cause extensive blood loss in smaller animals. They have a very painful bite, which can cause animals to be irritated, uneasy and even the gentlest of animals bad tempered.

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