Gnats (6495)

Certain species of adult black fly females are fierce biters, whereas others are strictly a nuisance by their presence around one's nostrils, ears, arms, hands, and other exposed skin areas. These flies can discourage people from remaining in or visiting certain recreational areas for fishing, camping, hiking, golf, etc. when the black fly season occurs. Children are especially susceptible and may be severely bitten while adults in the same area are scarcely aware of the flies. Most complaints in Ohio occur in early spring (April to June) in hilly areas with swiftly, flowing streams. Bites may appear where clothing fits snugly against the body, leaving a ring of bites just above or below the belt line.

After the black fly finishes feeding, bleeding may continue for some time. At first, the bite site appears as a small, red, central spot surrounded by a slightly reddened, swollen area. Next, the area becomes increasingly itchy, swollen and irritating, sometimes for several days. Some black flies readily attack people, whereas others prefer domestic animals or birds, often feeding during the daylight hours and sometimes into the night. Flies may become so abundant as to be drawn into the air passages of livestock, occasionally resulting in death. It is believed that allergic reactions to bites may be caused by histaminic substances in the fly's saliva. These flies transmit a disease of filarial worms, onchocerciasis, which causes blindness in people in Mexico, Central America and Africa in addition to protozoan parasites, leucocytozoonosis to turkeys and wild birds. They may be potential transmitters of encephalitis. It is suspected that the expansion of black fly populations in Ohio is likened to improvement in stream and river water quality in recent years. As with many aquatic insects, black flies are very sensitive to water pollution.

For more information, please visit this Ohio State University fact sheet.

Penn State Entomology Dept.

For more information on this subject, Please visit the College of Agricultural Sciences Publications Web site.

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