Flies are not usually associated with blood-sucking feeding behaviors, but some fly species inflict painful bites before sucking the blood from humans and many animals. Horse flies are probably the most well known of all blood-sucking fly species, but female deer flies also inflict painful bites before sucking blood. This feeding behavior raises concerns about this fly species’ potential for spreading disease, but research has not conclusively demonstrated that deer flies transmit disease to humans. However, there is one small exception.

Evidence shows that deer flies in the western United States can transmit bacteria that leads to a disease known as tularemia, which is also known as deer-fly fever or rabbit fever. Studies have also shown that a deer fly’s mouthparts and digestive system often contain viruses, bacteria, and protozoa. Although sustaining a bite from a deer fly is not likely to result in disease of any kind, the bites are reported as being quite painful. This is not hard to believe considering the anatomy of a female deer fly’s mouthparts. Female deer flies possess two blade-like features that lacerate skin, causing heavy blood flow out of the bite wound. This blood is then lapped up by a deer fly’s sponge-like mouthpart. Male deer flies possess similar mouthparts, only much smaller, and they are not capable of biting through human skin. Male deer flies do not suck blood like their female counterparts.

There exists 110 documented species of deer fly within the United States, all of which belong to the Chrysops genus. Deer flies, along with common house flies, belong to the Diptera order. Deer flies look similar to house flies, only they grow to be a bit larger in size. Deer flies typically grow to lengths between a quarter of an inch to a third of an inch. Deer flies are maligned for their swarming behaviors and their notoriously painful bites; and controlling deer flies with pest control strategies is impossible due to their widespread habitat. In fact, even powerful repellents like DEET are not effective at keeping deer flies at bay. The best and only defense against deer fly attacks are long sleeves and a heavy hat.

Have you ever sustained a bite from a deer fly?