Horse Fly


Actual Size: ¾  to 1 ¼”

Characteristics: Big, bulgy eyes and clear wings. Black or gray in color.

Legs: 6

Antennae: Yes

Wings: Yes

Habitat: Usually invades damp soil in low-lying pasture areas or near sources of water. Can be a big problem for farms with livestock.


  • Like deer flies, horse flies do not reproduce indoors. 
  • Capable of delivering a painful bite. 
  • Are particularly bothersome to livestock animals.

Horse Flies in Anaheim

Horse flies and deer flies are robust, sizable insects known for their relentless harassment of livestock and humans. Their blood-feeding habits can also lead to the transmission of disease-causing agents. True to their name, horse flies are infamous for targeting animals such as horses, cattle, mules, dogs, and even humans. Deer flies, which often bite humans, are relatively smaller in size, featuring distinctive dark bands on their wings and eyes that bear a resemblance to those of horse flies. Even a few of these flies can transform outdoor activities and work into uncomfortable and miserable experiences.

Horse Fly Habitat

Horse flies and deer flies often inhabit areas near bodies of water that are conducive to the development of their larvae. You may encounter these flies in brushy or low-lying pastures adjacent to creeks, streams, or water reservoirs that offer the moist soils required for their immature stages to thrive. To sustain themselves, both horse and deer flies employ a survival strategy of burrowing into the sand or gravel substrate near the water they’re infesting.

Horse Fly Behaviors, Threats, or Dangers

Female horse and deer flies possess the capability and willingness to bite humans, causing painful wounds that can occur on any part of the body. These bites often result in noticeable bleeding, though common first-aid-type skin creams usually help. Although rare, allergic reactions such as hives and wheezing can occur in some individuals. These flies are particularly troublesome for farms with livestock, as they mainly target large animals.