A dipterous insect of the family (Estridae, of many
   different species, some of which are particularly troublesome to
   domestic animals, as the horse, ox, and sheep, on which they deposit
   their eggs. A common species is one of the botflies of the horse
   (Gastrophilus equi), the larvae of which (bots) are taken into the
   stomach of the animal, where they live several months and pass through
   their larval states. In tropical America one species sometimes lives
   under the human skin, and another in the stomach. See Gadfly.