Horse Flies

Tabaninae horse flies are known for their size, and the painful bite inflicted by females.

Horseflies often live near water environments, where their larvae feed and grow on the local insects and small fish. Thinking habitat suggests that North American horsefly populations increase in the Southeast and decrease in the Southwest.

Adults can grow over an inch in length, and females feed on blood from mammals, including humans, a practice that places them into the insect pest category. For humans at least, the use of over the counter insect repellents containing deet (N-diethyl-meta-toluamide) is usually sufficient to deter them during their season. (Note: deet is a strong chemical and it should only be applied according to the directions given on the container.)

A couple dozen different horse fly species inhabit forests and fields across North America. Apart from size, many horse fly species can be identified by their colorful eyes.

Eye configuration can also help determine gender. The eyes of male horseflies are set close together, female horse fly eyes have a space between them.

The striped horse fly video presents both the male and female of the species, highlighting the eyes. Under typical weather conditions they fly North America's water edges year round in the south and summer in the north.

Picture two shows the female Western Horse Fly (Tabanus punctifer), a common Western species where the female's colorful eyes are muted. The light colored patch of hair behind the eyes serve as an additional species field identification clue.

Not to be outdone by blandness, the top picture shows the Black Horsefly (Tabanus atratus), a very common Eastern species.

Regardless of the bland color of the body and eyes for both the males and females, at one inch in size, the Black Horse Fly can be a real nuisance.

© 2009-2011 Patricia A. Michaels