are many species of Horse Fly in different genera. Many are large with
colourful or patterned compound eyes. One thing they have in common - the female needs blood to make her eggs, like the Mosquito, and she bites - like the Mosquito but a lot more painful. Some species prefer horses, cattle or deer but most will take human blood if available. The male doesn't bite.
The Common Horse Fly (Horsefly) above, also called a Cleg Fly and specifically the Notch-horned Cleg Fly, Haematopota pluvialis, has attractive, patterned brown wings and red, striped eyes.
Deerfly, Chrysops relictus, called the Twin-lobbed Deerfly to distinguish from other Chrysops Deerflies, is large with bright green, patterned eyes, patterned wings and black markings on fawn.
Another common Horsefly is the Banded-eyed Brown Horsefly, Tabanus bromius, above, with big, green-brown compound eyes (red bands close-up), clear wings and dark brown markings on fawn.
(A better candidate to be called "Notch-horned.")
Another Horsefly - yet to be identified.