Fungus gnat

Fungus gnats are small, dark, short-lived gnats, of the families Sciaridae, Diadocidiidae, Ditomyiidae, Keroplatidae, Bolitophilidae, and Mycetophilidae (order Diptera); they comprise 6 of the 7 families placed in the superfamily Sciaroidea.

The larvae of most species feed on fungi, decaying plant material, or plant roots, helping in the decomposition of organic matter; some species are predatory. The adults are 2–8 millimetres (0.079–0.315 in) long, and are occasionally pollinators of plants and carriers of mushroom spores. They also may carry diseases such as pythium (which causes "damping-off" to kill seedlings) on their feet.

Most fungus gnats are weak fliers, and can often be seen walking rapidly over plants and soil, rather than flying. However when airborne, the gnats may be quite annoying to humans by flying into their faces, eyes, and noses, both indoors and outdoors. These flies are sometimes confused with drain flies.

Some fungus gnats are exceptionally hardy, being able to tolerate cold conditions through their possession of antifreeze proteins. Typically, overwintering organisms can either avoid freezing or tolerate freezing, but Excechia nugatoria can do both. For E. nugatoria, the production of noncolligative antifreeze proteins (NAPs) protect the head and thorax from freezing, but they do not protect the abdomen. Freezing of the head and thorax in other insects tends to have adverse effects on neural tissue, so it is not surprising that these protective mechanisms have been observed in certain species, but E. nugatoria is the only insect known to semi-freeze through the winter, which may be an evolutionary advantage. According to Sformo, by allowing the abdomen to freeze, evaporative water loss is reduced over the course of the winter.

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