Stable flies are vicious biters often flying from host to host until their appetites are whetted. This habit of flying to many hosts makes them potential vectors of organisms causing diseases in humans. They will take blood from many animals including rats, cattle, horses, rabbits and man. Stable fly bites. Black flies are minute, stout bodied and humpbacked.
Preferred habitats are wooded coves along fast flowing streams.
The larvae are aquatic and feed on microscopic organic material in streams. Black flies swarm mainly in the early morning and evenings oftentimes completely surrounding people who are unfortunate enough to be where they are. Long distance host finding begins with flies detecting odors upwind. As they near the host, they orient to carbon dioxide emissions and within six feet they use vision. Black flies can discriminate between colors often preferring black, blue and green.