Are gnats attracted to eyeballs, or are those near our eyes simply the ones we notice most?
Mike Follows
Sutton Coldfield, West Midlands, UK
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The term gnat is a loose description for many species of tiny flying insects. I was surprised to learn that some entomologists exclude tiny biting insects like the black fly (Simuliidae) and biting midges (Ceratopogonidae) from their definition of what a gnat is.
Eye gnats, or eye flies, are part of the genus Liohippelates in the Americas and Siphunculina in parts of Asia. These are part of a biological family of insects known as grass flies, which are sometimes called frit flies (not to be confused with fruit flies).
It is eye gnats that are attracted to lachrymal secretions (tears). I can imagine that the irritation could be extreme enough to bring tears to your eyes, which is likely to make things worse.
The problem is that eye gnats are attracted to a variety of animal secretions, including dung, as well as open wounds. This means pathogens can stick to the insects, leading to the transmission of diseases like human acute conjunctivitis (pink eye), Brazilian purpuric fever and yaws, a skin infection seen in the Caribbean and parts of South America.
Eye flies can occasionally and inadvertently injure the eye. A 1976 study found that an eye fly (Siphunculina funicola) once became in the eyelid of a 15-year-old Indonesian girl, where it became entombed in a cyst.
They can transmit disease among animals, including acute bovine mastitis and vesicular stomatitis, which presents as akin to foot-and-mouth disease.
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