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Black Fly

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Black Fly

Black flies are common in humid, wooded regions in summer months and can be found throughout semitropical regions year round. Black flies are most active around sunset during June and July and act as severe nuisances to backpackers, hikers and other outdoor enthusiasts. Black flies are not active at night, nor do they live indoors.

Black fly larvae thrive in all kinds of flowing water, making them most common in creeks and waterfalls. Adults seek moist environments and may bite exposed skin such as the face. They may also find their way under belts and socks, although they are incapable of piercing through clothing. In order to avoid being bothered by black flies, hikers often tightly tuck in their shirts and pants.

These insects have proven to be such a nuisance in summer months that special hiking gear has been developed to combat them. Research also shows that black flies are more attracted to dark colors than to light colors; hikers who dress accordingly are less likely to be bothered.

In the wetter parts of the northern latitudes of North America, including parts of Canada, New England, Minnesota, and the Upper Peninsula of Michigan, black fly populations swell from late April to July, becoming a nuisance to humans engaging in common outdoor activities, such as gardening, boating, camping, and backpacking. They can also be a significant nuisance in mountainous areas.

Black flies are a scourge to livestock in Canada, causing weight loss in cattle and sometimes death.

Diseases Vectored by Black Flies:

River Blindness, Black flies are central to the transmission of the parasitic nematode Onchocerca volvulus which causes onchocerciasis, or "river blindness". It serves as the larval host for the nematode and acts as the vector by which the disease is spread. The parasite lives on human skin and is transmitted to the black fly during feeding.

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