Fungus gnats are small, dark, short-lived gnats, of the families Sciaridae, Diadocidiidae, Ditomyiidae, Keroplatidae, Bolitophilidae, and Mycetophilidae (order Diptera); they comprise six of the seven families placed in the superfamily Sciaroidea. Description The larvae of most species feed on fungi growing on soil, helping in the decomposition of organic matter. However some species are predatory, including those in the genus Arachnocampa of family Keroplatidae – the "glowworms" of Australia and New Zealand. The adults are 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. Hardiness 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) protects 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. By allowing the abdomen to freeze, evaporative water loss is reduced over the course of the winter. Management Fungus gnats in the family Sciaridae may be pests. They are typically harmless to healthy plants - and humans - but can inflict extensive damage to seedlings; their presence can indicate more serious problems. In houseplants, the presence of sciarids may indicate overwatering; they may be feeding on roots that have been immersed in water too long and are thus rotting, or the gnats may be attracted to fungus growing in saturated topsoil. Consequently, allowing the top two inches of soil to dry may reduce their numbers. The pests are sometimes also managed by placing a layer of sand pebbles, or indoor mulch on top of the soil around plants. Insecticides Pyrethrins and the similar pyrethroid compounds are known to have insecticidal properties,