–by Dr. Cassandra Olds, Livestock and Veterinary Entomology
Horn flies are most well known for being a cattle pest where high numbers can cause significant animal stress and production losses. Although seen much less frequently and in lower carrying numbers, horn flies can be bothersome to horses especially those grazing together with or near cattle. On horses, as with cattle these flies are found on the back of the animal, sometimes moving up the neck and down to the rib area. Horn flies will cluster together with their heads pointing down towards the ground as they feed. Each horn fly will take a small blood meal 20-30 times a day. When disturbed, horn flies will fly up briefly but settle back onto the animal quickly. If you suspect your horse may be playing host to a population of horn flies you can use fly spray on the affected area to remove them.
Photos by Cassandra Olds — Livestock and Veterinary Entomology