Fungus Gnat (Orfelia spp.)

Fungus Gnat (Orfelia spp.)

The Fungus Gnat (Orfelia spp., Mycetophila spp. etc.) is a very small mosquito-like insect in the order Diptera (Flies) very common around French Hill Pond. It is difficult to identify the species, genus and even family of a specific Fungus Gnat without a detailed microscopic examination of the wing patterns and other parts of this insect. The photographs on this page are likely of the common Fungus Gnat of the genus Orfelia. Although the photographs of this insect show an ugly and rather threatening creature, Fungus Gnats are harmless to humans and animals. However, they are attracted to carbon dioxide, which can cause them to swarm around people or animals. If they get into a house, they can become a nuisance. This insect may be the insect that some people call, "no-see-ems." They may be confused with Fruit Flies.

Fungus Gnats can be from ⅛ to ¼ inch (3 to 6 millimeters) long. They appear brown or black to the naked eye but microscopic examination will show light and dark markings as shown in the photograph above. The body and long, slender legs are hairy. The wings are smoky. They have large compound eyes, one of which is shown in the microphotograph below. In some species the eyes meet above the base of the antennae.  They are attracted to light and may be first noticed indoors as they congregate at windows.

Fungus Gnat (Orfelia spp.) Compound Eye

These insects live in decaying matter and fungus, whence their name. The larvae eat organic matter including parts of living plants. Therefore, they can be destructive of house plants. They do not normally enter a house in search of food but may be brought into the house in the soil of plants left outside during the summer but brought in during winter or in the soil of potted plants that was not properly sterilized. Outside, Fungus Gnats only reproduce during summer. One Fungus Gnat can lay up to 300 eggs at one time. Indoors, they will reproduce all year producing a large number of offspring.

Fungus Gnats can be controlled with pesticides but prevention is the best control. Avoid overwatering house plants and keep them indoors. Inspect plants you are considering for purchase for insect infestation. Use sterilized soil for potting. Fly traps can help control an infestation indoors.


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