Sciaridae (or sciarids) are small (1 to 11 mm), blackish, brownish or yellowish flies with wings that are often dark (sometimes small or absent) and relatively long feet. Their eyes are close together or joined in the shape of a bridge above their antennae – except in wingless species. Unlike mosquitoes, their proboscis (tube used to suck liquids) is usually short. With the exception of their eyes, their anatomy and behaviour resemble those of mycetophilidae (fungus gnats), and they were previously classified in the same group.
A small, white, translucent larva (maggot) with a black head hatches from an egg. It buries itself in the ground and feeds on root hairs and rootlets (at the root tip) as well as organic material. The larva then transforms into a nymph (pupa), then an adult. After mating, the female lays her eggs on organic material on the ground. Adults are attracted by light which is why they are often seen near windows. Although they are harmless to us, having them around can be annoying. They often dart across the floor. In some species, the larvae move about in great numbers.
Places where they can be found in the home
Sciaridae develop in the humus-rich soil used to grow ferns and indoor potted plants. When the larvae attacks the plant roots, the plants become weaker, turn yellow and lose their leaves. African violets, geraniums and poinsettias are the most frequently infested plants. These flies can cause significant damage in greenhouses and some mushroom cultures. Outdoors, sciaridae seek out moist soil, fungus and decomposing plant material. They can be found in moist, shaded places such as rotting wood, beneath bark on fallen trees, animal burrows, excrement (the larvae feed on it), bird nests and caves. They also eat insects captured by a pitcher plant – an insectivore.
Avoid over-watering plants.
Inspect the saucers under your flower pots.
Minimize the number of moist and shady places.
New soil could be sterilized to prevent introducing insects.
Larvae feed on the mildew that appears when plants are watered too much. You should therefore find the problem soil and dry it out. To do so, turn over the top 5 to 7 centimetres (2-3 inches) of soil and the larvae will die. You should also clean the saucers underneath your flower pots. Change your watering habits to prevent the problem from recurring. It is better to allow the soil to dry between waterings to prevent a population explosion. Larvae have been found in bird dropping where they feed on the mould. Excessive watering of nearby plants has also been a factor. Large fans and electric light traps have been used in combination with the previously described measures. Larvae have also been found in wall insulation foam where mildew accumulated.
Nematodes (worms) are predators for sciaridae larvae.
In some species, one female will produce only males while another will produce only females.
Even among Diptera (insects with only two wings), there is an impressive diversity of species. In spite of what you might think, not every tiny creature that lives alongside a human being is necessarily a mosquito that wants to attack him.
Since it is usually the winged adults that we see, it can be difficult to believe that the great majority of Diptera larvae (flies, mosquitoes, etc.) are found in moist or liquid environments.