Locally, horse-flies can be a serious nuisance because of their painful bite, and they can – at times – prevent a normal outdoor life for those who are allergic to the horse-fly … The horse-fly pumps rather large amounts of saliva into the wound. Those who suffer allergic reactions could be worse off. Horsefly bites are particularly painful and slow to heal compared to other insect bites. The mandible is essentially the insect’s jaw. For some people, this results in severe allergic reactions. The most distinguishing trait of the Horsefly is the eyes; they will be larger than a normal horsefly and be exceedingly colorful (generally a green). Horse fly bite symptoms MD Health cites the symptoms of a horse fly bite as pain, red lumps and inflammation and itchiness. This is because of the method that the flies use to bite. The wings, depending on the specific species, will be a solid color (black or clear). Log in, The active substances, venom, poison and saliva, Flea control in the surrounding environment, If the European pigeon ticks are not controlled, Infection and the spreading between animals. Meaning. If you’ve ever been bit by a horse fly, you know that it hurts. Generally the fly will be about 1 inch long (though it can range between ¾ … The fly’s mandible is what makes these bites so painful.