DIPTERA > NEMATOCERA | Lower Diptera

BIBIONOMORPHA > Sciaroidea > Mycetophilidae (c.500 species)

(subfamilies: Eudicraninae, Gnoristinae, Leiinae, Manotinae, Mycetophilinae, Mycomyinae and Sciophilinae)

As previously noted, Mycetophilidae is one of five morphologically closely related families that, together with Keroplatidae, Bolitophilidae, Diadocidiidae and Ditomyiidae, are collectively known as fungus gnats. There are around 575 species that have been recorded in Britain with the vast majority being classified as mycetophilids; commonly regarded as 'true fungus gnats'.

The adults of these species are typically found in damp, shady woodland locations. They are tiny to medium-sized flies, variable in form from slender to relatively stout, with long legs and well-formed elongate coxae that are placed closely together, which produces a vaulted thorax that gives them a distinctive hump-backed appearance. The body colour ranges from dull yellow to brown or black, with many species having a striped abdomen. The head is small with antennae usually comprising 16 segments, and the legs have long apical spurs on the tibia and often look spiny with rows of upstanding bristles. The wings are usually clear, although sometimes tinged or marked; venation is variable, which can help with identification of certain genera.

The sheer number of species makes identification very difficult and, in most cases, simply distinguishing an individual as a mycetophilid is probably as good as it's likely to get from photos.

As you would expect, given their scientific name, the larvae feed on or in various fungal fruiting bodies, as well as on fungal hyphae and spores, which means that they may also be found under the bark of decaying trees, on rotting logs or in damp leaf litter.  

Most species are white with dark heads, elongate and maggot or slug-like in shape, whilst others are dark-coloured and have a more extended worm-like appearance, very similar to the keroplatid larvae on the previous page. The latter are the web-spinners of the subfamily Sciophilinae, aptly referred to as 'slime travellers' by one author. But, there's another very different globular form that look more like blobs of jelly that could almost be mistaken for slime mould if it wasn't for the fact that a tiny head appears now and again. Their unusual shape is created by their body being covered in frass within a protective mucus membrane; a variation of a technique used by a few other insects, such as lacewing larvae, to disguise their appearance and make themselves less appealing to any would-be predator. This larval form is only known in two genera, Epicypta and Phronia from the Mycetophilinae subfamily. The relatively consistent shape and pale yellowish-brown colouration of the former, of which there are only four species, is quite distinctive but, in Phronia where there are over thirty species, there are various adaptations. Some adopt the same technique as Epicypta, having similar appearance, but generally being much darker in colour, whilst others adorn themselves with frass without the addition of any mucus which hardens into a conical shape. I have not seen this particular form, but I have photographed some of the blobs as can be seen below.

A further bit of related information for future reference is that the more conventional forms of mycetophilid larvae can be distinguished from keroplatid species by having their external respiratory spiracles on the prothorax as well as body segments 1-7. Keroplatid larvae do not have spiracles on their body as they have an entirely different respiratory system.

Footnote: whilst I would always seek help and/or confirmation regarding species that I'm unable to identify as I had to do here, any associated information, such as that given above or on the previous page in respect of the larvae, is my interpretation and understanding from what I've read. I hope it's accurate and informative for anyone who has stumbled upon these particular pages, but it's primarily written as an aide-memoire for me. It will be continually reviewed and, if necessary, revised as my knowledge increases.

New family added, June 24 (v.1)