Female blackflies, requiring blood to lay eggs, bite humans and animals, while the male blackfly feeds on plant material. Blackflies are a nuisance and cause itching bites. When present in large numbers, they fly into the ears, eyes, nose and mouth. They are attracted to animals by the carbon dioxide and moisture present in exhaled breath, by sweat and by dark colors. In some cases they can even cause the death of animals by suffocation and loss of blood.
Blackflies are a vector for diseases of humans, turkeys and wild birds.
Blackflies lay their eggs in running water, where the larvae develop into pupa and eventually become adults. Control of blackflies include temporarily damming running streams, eliminating vegetation from the stream, and chemical treatments.