Under certain conditions, though, which depend on the nature of the growth medium, the health of the plant and the population density of larvae, they may attack the living plant tissue. Though they do eat plants, the larvae go for perishing or weakened tissue by choice. Their diet is mostly rotten and mouldy material: they enjoy rotting plant or animal tissue, fungi and soil algae. It is the larvae which cause the damage, during the 2 or 3 weeks that they feed. At 24✬ (75☏) the cycle from egg to adult takes 21 days at 16✬ (60☏) it takes 40 days. These development times depend on temperature. A week later, the adults emerge, to live for 4 to 10 days. The pupa stage is in the soil or the growth medium: the pupae are 3 to 6 mm and are coloured between light chestnut-brown and grey. They take from 24 to 27 days to develop, over 4 larval stages. The legless larvae measure 5 to 8 mm, with a white translucent body and a black head. They hatch 9 to 12 days later if the temperature is 15✬ (59✯). These eggs are very small (0.09 to 0.15 mm) and white/yellow. They have large veined wings which enable them to move fast, with a random, darting flight.Ī few hours after appearing, the female mates, and three days later lays from 100 to 200 eggs in damp places on the ground near rotting vegetation. These adults feed very little during their lives, which may last a few days. It prefers dark places, flies near ground level, and may appear at any time of year. In shape it rather resembles a mosquito, with a prominent thorax. The adult is a little gnat, dark to black in colour, from 2 to 5 mm long. This is the pupa, which gives rise to the adult after metamorphosis. At the end of its development the maggot becomes immobile and takes on a barrel shape. The larva is usually called a ‘maggot’ it has a typical cylindrical-conical shape, no legs, and mandibles reduced to two mandibular hooks. The Diptera are insects that metamorphose, or alter shape, completely. > Life cycle and general description of fungus gnats The adults themselves generally do little harm it is the larvae that do the damage. Gnats enjoy the damp places in the glasshouse. The particular species at work may be relatively hard to tell apart exactly.īradysia paupera is the species most often found under glass. Fungus gnats belong to various genera in the Sciaridae family: Bradysia, Sciaria, and Lycoriella. Insects of this order are easy to recognise by their single pair of wings. This glasshouse pest is a small member of the order Diptera. Healthy adult plants, on the other hand, are seldom affected by this pest.
In moist, heated glasshouses seeds, seedlings and young cyclamen plants are often subject to attack from various species of gnat.
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