Midge. Coloured scanning electron micrograph (SEM) of a midge. 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. They readily bite humans causing irritating, painful, and, in some cases, long-lasting, lesions. Biting midges do not transmit diseases to humans but scratching of the bites may lead to secondary bacterial infection. Magnification X20 when printed at 10cm wide.