Horse fly

Horse flies (also called March flies and Deer flies) are any of several species of largish flying insects order Diptera, that inflict a painful bite on mammals. The term most often refers to specimens in the family Tabanidae, the largest of the true flies, the females of which bite, blast them.

Unlike smaller members of the order, horse flies are comparatively slow-moving and louder (their hum is more audible and in a lower range than that of small flies) so, if one is paying attention, one can wait for them to light and then swat them. Unfortunately, when distracted by on concentrating on something else, a human might ignore peripheral sounds and only become conscious of the fly after it has bitten; a startled human can aggravate matters with a self-inflicted slap! For patient humans, the pain of the bite is somewhat mitigated psychologically by the satisfaction of having killed the attacker.