Similar to ticks, black flies live off the blood of other animals, plus they can deliver painful bites! Irrespective of being a general nuisance to humane, these flies can hold diseases. Many U.S. states will have programs to manage black fly populations. Along with hurting immediately, black fly bites remain painful, itch, and certainly will become infected with scratching. Some people have allergy symptoms to these bites that include hives or wheezing.