The Sciaridae are a family of

flies Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced m ...

, commonly known as dark-winged fungus gnats. Commonly found in moist environments, they are known to be a pest of mushroom farms and are commonly found in household plant pots. This is one of the least studied of the large Diptera families, probably due to the small size of these insects and the similarity among species. Currently, around 1700 species are described, but an estimated 20,000 species are awaiting discovery, mainly in the

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also refer ...

. More than 600 species are known from

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

Description

Adult Sciaridae are small, dark flies 1-11 mm long and usually <5 mm long. They have a characteristic wing venation: there is no cross vein except for a short rs at the wing base, the anterior veins are a short R1 and a long R5, vein M has a simple fork with a long stem, and CuA1 has a fork with a short stem. Larval Sciaridae are slender and lack legs. They are white except for a black head, and their skin is slightly transparent so the contents of the gut are visible.

Distribution

The Sciaridae occur worldwide, even in extreme habitats such as

subantarctic The sub-Antarctic zone is a region in the Southern Hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° and 60° south of the Equator. The subantarctic region includes many islands ...

islands and mountainous regions above 4,000 m. Others (such as '' Parapnyxia'') are found in deserts, where they dig into the sand at extreme temperatures. Several species live exclusively in caves. However, most species live in forests, swamps, and moist meadows, where they live in the foliage. They are also often found in flowerpots. In moist and shadowy areas, up to 70% of all dipteran species can be Sciaridae. They are distributed through wind and drifting, for example on dead wood, and are often introduced by humans, by means of transported

humus In classical soil science, humus is the dark organic matter in soil that is formed by the decomposition of plant and animal matter. It is a kind of soil organic matter. It is rich in nutrients and retains moisture in the soil. Humus is the Lati ...

or similar.

Life cycle

The life cycle of only a few species has been studied in any detail, mainly those which are pests of commercially grown

mushroom A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is ...

s. Sciarid

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

e often occur in decaying plant matter such as rotten wood or under the bark of fallen trees, but can also be found in animal

feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a rela ...

or fungi. The species ''Austrosciara termitophila'' is an

inquiline In zoology, an inquiline (from Latin ''inquilinus'', "lodger" or "tenant") is an animal that lives commensally in the nest, burrow, or dwelling place of an animal of another species. For example, some organisms such as insects may live in the h ...

in termite nests while the genus ''Vulagisciara'' is a guest in ant-plants of family

Rubiaceae The Rubiaceae are a family of flowering plants, commonly known as the coffee, madder, or bedstraw family. It consists of terrestrial trees, shrubs, lianas, or herbs that are recognizable by simple, opposite leaves with interpetiolar stipules a ...

. Also, some species mine in plant parts above and below the earth. The larvae play an important role in turning forest leaf litter into soil. Adult females lay about 200 transparent eggs (each about 1 mm; " long) into moist soil. After about one week, the larvae hatch. About 90% of the larvae are female. Up to 2,500 per m² (230 per sq. ft.) can be found. Several species, especially '' Sciara militaris'', can be found to migrate in processions of up to 10 metres, containing thousands of individuals. These processions occur from May to June in central Europe. Occurrences have been reported e.g. in Southern Poland, the Polish name of the phenomenon is "pleń". The larvae there pupate from July to August. The adults with their characteristic dancing flight do not bite. They only ingest liquids and live only long enough to mate and produce eggs. They die after about five days.

Mating and genetics

Sciaridae practice paternal genome elimination, whereby the male passes on only the genetic material of his mother to his offspring. The functional result of this is similar to haplodiploidy, but via a very different mechanism.

Evolution

Sciarids are fairly common in

amber Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In M ...

deposits, with the earliest known

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s dating from the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

period.

Pest status

Sciarid flies are common pests of mushroom houses and of plants grown in protected culture, for example herbs, where the warm and moist conditions favour their rapid development. In commercial mushroom houses, sciarid fly larvae tunnel into the stalks of the mushrooms, and feeding damage can sever developing mycelium, causing mushrooms to become brown and leathery. Their faeces may also prevent the mycelium from colonising the casing layer, severely reducing yields. As a pest of plants, sciarid larvae feed on the root system. In both industries, adult sciarid flies are a nuisance pest that can result in crop rejection if high numbers are present in the growing area. The damaging larval stage can be controlled using the beneficial

nematode The nematodes ( or grc-gre, Νηματώδη; la, Nematoda) or roundworms constitute the phylum Nematoda (also called Nemathelminthes), with plant- parasitic nematodes also known as eelworms. They are a diverse animal phylum inhabiting a bro ...

''Steinernema feltiae'', which enters the larva and releases a bacterium (''

Xenorhabdus ''Xenorhabdus'' is a genus of motile, gram-negative bacteria from the family of the Morganellaceae. All the species of the genus are only known to live in symbiosis with soil entomopathogenic nematodes from the genus '' Steinernema''. Although n ...

'' sp.) that kills the insect. The nematode then reproduces within the larva and its young are released into the growing medium, where they actively search out new host larvae (infective juveniles).

References

Expert website
(Frank Menzel)

* This page incorporates information from the German Wikipedia.

External links

* 1820: ''Enumeratio insectorum in Museo Gust. Joh. Billberg'' (4) p. 121. G. J. Billberg, Gadel

* *
Fungus Gnats Online

on the University of Florida, UF / IFAS Featured Creatures Web site
Diptera.info Gallery Images
{{Taxonbar, from=Q582991 Agricultural pest insects Insect pests of ornamental plants Nematocera families Articles containing video clips Extant Cretaceous first appearances