Cluster Flies are similar in size to the House Fly, about 3/8-inch. They are non-metallic gray and their wings completely overlap their backs. Their larvae are never seen because they develop as parasites in earthworms. The female flies mate in the spring and leave their eggs in the soil. The eggs hatch in three days and the larvae then burrow into the bodies of the earthworms, and that is where they develop. The development stage for the Cluster Fly requires 27 to 39 days. They enter structures in early fall to seek warmth and shelter from the cooling temperatures.

Fungus Gnats are very small flies 1/32 to 7/16 inch long and has the appearance of a mosquito. They are usually black, yellowish or brown. The dark winged fungus gnat has smoke colored wings. The larvae will actually molt four times. The eggs hatch within a few days.

These gnats are small enough to pass through typical structural screening. The adults are usually more active and visible at dusk and are usually found near the breeding site. The fungus gnat prefers to seek out dark moist undisturbed places to rest and nest.

The Fruit Fly is considered a nuisance fly rather than a pest, since most species breed in rotting material such as thin-skinned fruit, like raspberries and cherries and can be a serious agricultural pest. The adult flies are 1/8 inch long and dull yellow brown with two horn like stalks at one end. The eggs are laid onto the surface of fermenting fruit or vegetables, or areas where moisture and yeast are abundant. The eggs hatch within 30 minutes. Each female produces up to 500 eggs. The larvae complete development in 5 to 6 days.

The Drain Fly is very small, delicate and hairy. They are about 1/16 to 1/4-inch long. They are usually brownish grey or black. They have white speckled and pointed wings. The body and wings are covered with long dense hairs. They breathe through a hardened stalk-like siphon tube at the end of their body.
The females lay 30 to 100 eggs in the jelly like film that covers rocks and stones in sewage areas. The eggs hatch in about two days. In 9 to 15 days the larvae will complete development. The larvae will feed on fungi, algae, sludge and bacteria. The adults live up to two weeks.