Deer & Horse Fly Information

Deer Flies and Horse Flies


Horse flies and the smaller deer flies belong to the fly family called Tabanidae. They are notoriously fierce biters.  Their bite is painful, slow healing and can be a memorable and unpleasant experience  . . . worst of all most deet-only based repellents available locally do not have a reputation for stopping attacks from these flies.  Until you are bitten by one of these flies you really can’t appreciate the description of “an ice pick bite”.


Protection Methods – composite repellents such as Sawyer Broad Spectrum that contain R326 (a fly repellent) and deet will do a better job than deet-only products.  This product is often used for protecting horses as well as their riders. 


Permethrin is also used on clothing and can protect from bite through.  Sawyer Clothing, Duranon, Bens Clothing and JT Eaton 209 are brand name formulas for clothing and are available in 6 oz aerosols and larger trigger spray applications.  The JT Eaton label includes veterinary uses for dogs and livestock.  A concentrate for veterinary use (V2) that is labeled for horse and other animal use is also available.


Fly Traps – a new addition in our fight against these flies is the Deer Fly Trap Patch.  This new non-chemical fly attractant is applied to the back of your hat and when flies attack, they’re captured on the special adhesive.  Please note that after a day outside your hat should not be worn to dinner. The flies stuck onto the trap are not very appetizing.  We have had very good reports from outdoors professionals on this product.  Not recommended for those that wear their hair long.


Protective Clothing – special garments made of no-see-um midge netting can offer a comfortable non-chemical protection to the wearer. 


First Aid – the use of a Sawyer Extractor Pump to remove fly saliva/anticoagulant can have benefits to the victim with respect to the speed and comfort at which the wound heals.  Faster healing with less itching is a big plus with these bites as well as the bites of other insects such as black files and mosquitoes.  The sooner after the bite occurs that the Extractor Pump is used the better the results. The use of a bite relief/antiseptic will offer additional benefits to healing. 


Use the search term FLY to review products that can address this problem.


Injury - These flies are mostly a nuisance although they can cause injury and long lasting discomfort.  Because of the anticoagulant dispersed during their bite excessive bleeding can occur and secondary infection is a possibility.


The flies cut the skin with their razor like mouthparts.  If unchallenged these flies can suck blood for up to several minutes during which they deposit strong anticoagulant to keep the wound from clotting. The wound from the bite is slow to clot and may continue to bleed attracting other blood feeding insects.  There are potential infections associated from such bites caused by the initial and secondary feeding insects.  Some victims suffer severe lesions, high fever and even general disability when bitten.  Allergic reactions may occur from the saliva and anticoagulant cocktail delivered during the bite.


Pets should be protected from these flies.  Just because they are silent does not mean they don’t suffer the pain and discomfort from the tortuous attacks of these relentless insects.  


The Villain – the horse fly is a thick bodied, broad-headed fly with large bulging eyes.  The horse fly can measure from ¾” to 1” and fortunately is less common. These large horse flies are brown to black in color and have varying triangles/strips on the abdomen. A smaller more common species found near beaches is the “greenhead fly”.  Their brilliant green eyes are the most obvious identifier. They are strong, fast fliers that land softy and bite quickly.


The deer fly compares in size to the common housefly.  They are soft bodied and have colorations of mostly yellow or black with abdomen patterns.  Their wings are marked with dark patterns.  They have brilliantly colored eyes that range from green to gold. They too are strong, fast fliers that can land softy and bite quickly.


The females bite and suck blood. Horse flies are all well known for a nearly silent flight. They land quietly on exposed skin and give a painful almost ice pick level bite. They feed on mammals, large and small, including people. When the female bites, her saliva contains a strong anti-coagulant. The anticoagulant in the saliva prevents the blood from clotting so that she can feed quickly. A small animal may even bleed to death if attacked by large numbers of horse flies or deer flies.  The resulting wound heals slowly offering opportunity to other blood feeding insects to instigate additional infection potential.  Fast use of first-aid to remove the saliva/anticoagulant is an important step.


Male horse flies and deer flies feed on the nectar and pollen of flowers and do not bite.


The female of both species lays her egg clusters on leaves or plants overhanging water. The larvae hatch and drop into the water to continue development. The larvae are aquatic and move about the plants and pond bottom eating small aquatic insects, worms, snails, and tiny animals. 


Use the search term FLY to review products that can address this problem.