Horse-flies or horseflies (for other names, see common names) are true flies in the family Tabanidae in the insect order Diptera. They are often large and agile in flight, and the females bite animals, including humans, to obtain blood. They prefer to fly in sunlight, avoiding dark and shady areas, and are inactive at night. They are cosmopolitan, with only a few isolated islands and polar regions uninhabited. Horse-flies have appeared in literature since Aeschylus in Ancient Greece mentioned them driving people to madness through their persistent pursuit.