DIPTERA > NEMATOCERA | Lower Diptera

BIBIONOMORPHA > Sciaroidea > Keroplatidae (51 species)

(subfamilies: Keroplatinae and Macrocerinae)

Keroplatidae, Bolitophilidae, Diadocidiidae, Ditomyiidae and Mycetophilidae are five closely related families that were formerly all grouped together, but have now been taxonomically separated. The species within all of these families are collectively known as fungus gnats. They are classified within the Sciaroidea superfamily together with the Sciaridae black fungus gnats and the Cecidomyiidae gall midges.

The Keroplatidae family comprises fifty-one, medium to large, 4-15mm, mainly slender-bodied species that are partially distinguished by having relatively uniform wing venation where the r-m crossvein is replaced with a short R-M fusion. The head is small with mouthparts that are sometimes elongated; ocelli present; eyes dichoptic; antennae with at least eight segments that are either shortish and flattened or, in the Macrocerinae species, long and slender; the thorax is vaulted; the wings are broad, either clear or with markings; and the tibia have apical bristles or spurs.

Adults are usually found near the larval habitats, typically in moist and dark areas of woodland.

To date, I'm only able to confidently feature a single representative individual from this family, which was identified by an expert on the UK Diptera FB group. The NBN Atlas indicates reasonably widespread, although scattered, distribution for Platyura marginata, primarily centred around the south east and the Welsh borders but also, for some reason, heavily concentrated in north Wiltshire, Shropshire and Gloucestershire. There's only a single old record from Dorset and, as far as I can see, none from south Hampshire. In fact, when I checked in June 24, there hadn't been any recorded sightings of any Kerplatidae species locally for over ten years, which just goes to show how under-studied this group is.  

Interestingly, only the larvae of the three members of the small Keroplatini tribe are regarded as true mycophagous species. They are spore feeders that are typically found living on the underside of bracket fungi. These species spread a mucous film across the hymenium that provides shelter as well as acting as a sheet-web to catch spores. The remaining species are primarily associated with decaying wood or leaf-litter. Although some larvae within the Orfeliinini (Keroplatinae) live on or in rotten wood where they feed on mycelia, the majority of the twenty-six species in this tribe are predatory to some degree; as are all the twenty-two members of the Macrocera genus (Macrocerinae). These carnivorous species construct web-like nets that they cover with sticky secretions containing salicylic acid to catch various small invertebrates on which they can feed. The webs vary depending on the space available, but usually consist of a system of crossed lines bearing droplets of saliva. Separate to the feeding web there will usually be another, often tube-like, structure where the final instar larvae will pupate.

Some of these species even glow, emitting a blue light that is supposed to attract prey. I haven't, as yet, seen any of these bioluminescent forms as they mainly occur in more tropical areas, but there are a couple of examples that have been recorded in Britain. Keroplatid larvae are quite distinctive once recognised although, that said, I have to admit that when I first saw one, I thought it was an enchytraeid pot-worm until I realised it had a head capsule.

Updated, June 24 (v.2)