The flies bite by cutting into the skin and feeding on the pool of blood that forms in the hole they make. Anticoagulants injected into the feeding site by black flies can cause mild to severe allergic reactions in sensitive individuals. Strong reactions include fever, nausea and allergic dermatitis. Large black fly populations and strong bite reactions can be life threatening and have been reported to kill domestic animals. Black fly bites are very painful because of the hole that is cut in the skin, the anticoagulants and other materials that are injected, and the immunological differences between insect and hosts tissues.
Some people are very attractive to black flies and have strong feeding reactions.
Others appear to repel black flies and are bitten little if at all. Although S. slossonae is primarily a bird feeder, large swarms are attracted to people. Fortunately in Florida, most of the black flies attracted to people do not bite. Anyone showing strong allergic reactions should consult a physician for immediate treatment. Management Control of black flies is difficult because of the number of potential breeding sites.