Horn Flies

Facts, Identification, & Control

Scientific Name

Haematobia irritans


What Do They Look Like?

  • Color: Horn flies have brownish-red heads and dark colored bodies.
  • Size: Their bodies are about 3/16 of an inch long or can be about half the size of a common house fly.
  • Characteristics: These insects have dark, shiny bodies with somewhat overlapping wings covering their abdomen. They have small heads, downward-pointing antennae, and have striped thoraxes on top.

How Did I Get Horn Flies?

Since horn flies feed almost exclusively on blood from cattle and horses for food and livestock waste to breed, they are attracted to farms and ranches. People who don’t raise livestock have little reason to worry about these pests.

How Serious Are Horn Flies?

Horn flies are vectors of several disease-causing pathogens including filarial nematodes that cause stephanofilariasis, a dermatitis characterized by areas of crusted skin on the underside of cattle.

Horn flies deliver painful bites that may cause bacterial infections in open wounds. These flies only bite humans or pets on occasion. These pests require their livestock hosts to constantly defend themselves from these bites. This tires these animals out, leading to exhaustion and health concerns.

Horn flies are one of the most important cattle pests, causing over $1 billion in economic losses each year and cause health-related effects to cattle including:

  • Damage to cattle hides resulting in poor quality leather
  • Loss of milk production
  • Weight gain in dairy and beef cattle

Signs of Infestation

Adult horn flies are easy to identify from their large swarms feeding on livestock.

How Do I Get Rid of Horn Flies?

One technique to control horn flies are walk-through traps. These traps prey on horn flies hesitancy to enter a dark building. As cattle move into the large trap, flies leave the animal and are then trapped or killed by sticky traps or electrocution.

Another way to trap these pests is to set controlled fires in pastures. Since fires are set during their dormant season (late winter and early spring) alter the cow manure pats and helps reduce the number of pupae that are overwintering in or below them.

Horn flies are usually killed by exposing them to insecticides contained in:

  • Animal ear tags
  • Pour-on preparations
  • Sprays
  • Dust bags
  • Back rubs

What Orkin Does
Your local Orkin technician is trained to help manage horn flies and similar pests. Since every building or home is different, your Orkin technician will design a unique program for your situation.

Orkin can provide the right solution to keep horn flies in their place and out of your home or business.


Behavior, Diet, & Habits

Horn flies are one of the most serious cattle pests throughout the United States. These pests collect on cattle, often gathering on the back and sides of the animal. They sometimes congregate around the base of their horns, this is why they are called horn flies.

During hot and sunny weather, they may move downward onto the animal’s belly. Adults generally prefer to settle on the backs of cattle during the cooler part of the day and on the belly during the hotter part of the day. Since both male and female horn flies are blood feeders, they cause pain, annoyance and interfere with feeding, resting and other normal livestock activities.

Horn fly populations peak in the early summer months, but decline as the temperatures increase during the hot and dry months. As the fall months approach and temperatures decrease and humidity and rainfall increase, populations will peak again.

Life Cycle

Horn flies have short life cycles, multiple generations per year, and a large number of flies that are fertile females. The life cycle from egg to adult takes about 10 to 20 days, depending on environmental conditions. They have a short pupation period, so their populations can easily grow until there are several hundred insects per animal.

The female lays all eggs to contribute to their ability to produce large numbers of flies. During her lifetime, a healthy, well-fed female adult can lay about 400-500 eggs. They are laid exclusively in fresh cattle manure.

Larvae hatch from eggs in about one day and feed on manure, passing through three larval stages in about 3 to 5 days.

Pupae develop from larvae and it takes only about 3 to 5 days for pupae to develop into mature adults.

Newly emerged adults mate on hosts and begin feeding. If no host is found, newly emerged adults can travel several miles searching for a host.