is a family of very small flies
, forming the bulk of those species known as fungus gnats
. There are approximately 3000 described species in 150 genera but the true number of species is undoubtedly much higher. They are generally found in the damp habitats favoured by their host fungi
and sometimes form dense swarms.
Adults of this family can usually be separated from other small flies by the strongly humped thorax but identification within the family between genera and species generally requires close study of microscopic features. The terrestrial larvae usually feed on fungi, especially the spores and hyphae, but some species have been recorded on mosses and liverworts. The larvae of some species, while still being associated with fungi, are at least partly predatory.
Delicate flies with the head hidden from above by the humped thorax. Anterior wing venation stronger than posterior.
Adult Mycetophilidae are slender-bodied, slender-legged flies. The antennae which are long and threadlike (non-aristate) are 8–16 segmented. There are three ocelli and the eyes do not meet. The maxillary palps are 3–5 segmented and droopg. The wing is without a discal cell; without a sub-apical cell and without a closed anal cell. The costa does not extend around the entire wing. A sub-costa is apparent; reaching the costa independently of vein 1 (e.g., Orfelia), or terminating short (e.g., Mycetophila). The leading edge veins are markedly stronger than the rest and vein 7 is present, reaching the wing margin. The lower calypter is much reduced or absent and the wings patterned or unpatterned. The tibiae all have a pair of apical spurs. Tarsi without a triple pad. Abdomen constricted basally. These and other terms are explained at
The Larvae and pupae. Larvae are eucephalic. Pupa without a puparium.
Around a dozen mycetophilid species are unique among flies in displaying bioluminescence . In some species this is restricted to the larval stage but in others this feature is retained by the pupae and adults. It has been suggested that the ability to produce their own light is used by some predatory larvae as a lure for potential prey, although it also obviously makes themselves more susceptible to predation or parasitism. These are not true Mycetophilids, but belong to the family Keroplatidae.
Mycetophilids, including some extant genera, are well represented in amber
deposits and the group appears to have been well established and diversified by the Cretaceous
period at the latest.
Some 800 species (including some of the bioluminescent species) have been split into a separate family by Tuomikoski in 1966, Keroplatidae
. This split is not universally recognized as yet and many sources still include the keroplatid genera within Mycetophilidae. Other recent families,included here in Mycetophilidae as they are not recognized by all workers are Ditomyidae
. The Mycetophilidae in this inclusive (widest)sense contain about 330 described genera. These include :