( Latin: Psychoda alternata )
These are small, dark flies which can some- times be seen on the walls and in the basins in bathrooms and lavatories. They belong to a group known generally as owl midges.
Their wings are hairy and relatively large, but they do not fly particularly well. They move by a kind of hopping flight, or simply walk around.
The eggs are laid in the slime that accumulates in water-traps and outlets of basins. The larvae live in this coating of slime, which is continually damp but not covered with water the whole time, and they feed on any organic matter present and on bacteria, algae and fungi.
These little flies are naturally rather annoying to have around but they do not sting nor do they cause any damage. In the filters of purification plants they can be regarded as beneficial, because there the larvae help to break down organic waste. In the house they are best controlled by removing the slimy deposit that the larvae live in. This can be done by pouring boiling water into the outlets and water traps. A watch should also be kept on the overflows of basins as these provide excellent living conditions for the larvae.