Sciophila fractinervis

Sciophila fractinervis is a tropical species and was originally described in 1940 by Frederick Wallace Edwards using specimens collected by Friedrich 'Fritz' Plaumann from the neighbourhood of Nova Teutonia, Santa Catarina, Brazil.[1] S. fractinervis has been found on cultivated greenhouse plants in the United Kingdom[2] and was recorded by Peter J. Chandler in 2010 on examples of commercially-grown Eustoma grandiflorum from Warwickshire. [3] This species was also recorded on greenhouse examples of Platycerium and Beaucarnea in the Netherlands in 2005.[4] S. fractinervis is considered by RINSE (Registry of non-native species in the Two Seas region countries) as a non-native species in Great Britain, France, Belgium and the Netherlands.[5]

Wing of the fungus gnat Sciophila fractinervis (male lectotype specimen, NHMUK010626504 BMNH258029).

The larvae of Sciophila fractinervis are brown in colour and have a glossy appearance, due to being enclosed in a mucus tube created from labial glands around the mouth.[2]

The adults have a dark grey head with a yellowish face, a yellowish thorax, brown abdomen and yellow legs.[1][3] The mouthparts are black.[1] The wings of the male measure 2.5 - 2.7mm and the wings of the female are 2.9 - 3.2mm.[3][4] Females of the species have shorter antennae than males.[1]

Edwards observed that the macrotrichia (hairs or bristles) on the wings of S. fractinervis are less dense, and therefore more conspicuous than on the comparable species Sciophila ciliata.[1]

Sciophila fractinervis larvae build silky cocoons of webbing either on the basal leaves of their host plant or on the soil underneath.[3] The larvae eat fungus spores which grow upon the webbing to sustain themselves, mainly from saprophytic species of fungus that feed on decaying plant matter.[2] The webbing built by the larvae likely also provides a protective environment against predators as larvae have been observed retreating when the webbing is suddenly vibrated.[2] The leaves of the host plant do not appear to be damaged by the larval activity, at least in cultivated plant examples[2][3] but the webbing is considered unsightly by commercial plant growers.[2] The larvae take about 7-10 days to pupate and emerge as adults.[3][2]