What Bug Is That? The guide to Australian insect families.

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A small family, treated by some authorities as a subfamily of Oestridae. In Australia we have only the three introduced species of horse botfly: Gasterophilus intestinalis (De Geer), G. nasalis (L.), and G. haemorrhoidalis (L.).

All three species live as larvae in the gut of horses. The mature larva is passed in the dung to pupate in the soil. The female lays her eggs attached to hairs on the horse's body, from where they are licked off by the horse.


The adults have vestigial mouthparts and adundant, long silky hair; the females have the end of the abdomen considerably attenuated. The antennal arista is bare, vein M is straight, vein Sc simply curved, and vein A1+CuA2 continued to the wing margin. The subscutellum is well developed as in Tachinidae.


Occurring widely in association with the host.

  • Gasterophil sp.