Pest Guides

Horse Fly

Family Tabanidae

Appearance

Horse Fly

  • Adult Horse Flies can be up to 25 mm in length.
  • Horse Flies are black to dark brown in colour with green or black eyes.
  • The males have contiguous eyes, which easily differentiates them from females where in which the eyes are widely separated.
  • A Horse Fly’s bite can be very painful. Unlike insects that pierce the skin, Horse Flies have mouth parts that work like miniature knives, which they use to slash open the skin with a scissor–like motion.

Lifecycle

  • The eggs of Horse Flies are laid in masses ranging from 100 to 1000 eggs on a vertical surface, overhanging water or wet ground favourable to larvae development, and hatch in 5–7 days.
  • Horse Flies hibernate in the larval stage and pupate during spring and early summer.
  • The adult life cycle of a Horse Fly is 30 to 60 days.

Habits

  • Mating is initiated in the air and completed on the ground where the female then deposits an egg mass, - sometimes with a shiny or chalky secretion, which aids in protection against water.
  • The male Horse Flies are mainly pollen and nectar feeders.
  • Tabanids are most active during daylight hours.
  • As with mosquitoes, it is the female Horse Fly that is responsible for biting.
  • Relentless attacks on livestock can result in reduced weight gain.