Fang flies are abnormally large flies that live in swamps. They have long proboscises which they use to feed on the blood of larger animals. They attach to the animal, and puncture the skin with the proboscises. If you try to pry one of these off of an animal, you will most likly rip the proboscis off of the fly's body, leaving the animal with a open wound which can be easily infected. The best wasy to remove a fang fly once it latches onto an animal is with open flame or intense heat.