1) British gadfly 2) Clegg 3) Gadfly 4) Horse fly 5) Horsefly 6) Swift fly 1) Clegg 
horse-fly
• (n.) A small breeze or horsefly.
Cleg noun [ Northern Eng. & Scot. gleg : confer Gael. crethleag .] (Zoology) A small breeze or horsefly. [ North of Eng. & Scot.] Jamieson. 
The cleg (clegg, breeze-fly, gad-fly) is a name applied to the members of the insect family Tabanidae, which are flies furnished with a lancet-like proboscis, of powerful flight, and a habit of sucking blood. It is only the female which sucks blood, and in some examples - such as the Hadrus lepidotus of Brazil - they may inflict wounds which bleed ...
Another name for horsefly