Midge eye. Black and white scanning electron micrograph (SEM) of part of the head of a midge, showing a compound eye. The eye is formed from numerous lens structures known as ommatidia. Most families of midges are non-biting. Biting midges feed on warm-blooded vertebrates and may be a nuisance to humans who are often in the field. Magnification: x300 when printed 10 centimetres wide