Although many insects are commonly called flies, true flies are members of the order Diptera. They are distinguished by having only two wings with which to fly and two balance organs called halteres. Diptera contains an estimated 1,000,000 species. These include such pests as houseflies, drain flies, and mosquitoes.
Houseflies are normally dull gray, with four dark stripes on the side of the thorax. Typically, between a quarter and half an inch long, they are a familiar sight almost everywhere around the world.
Several species of fruit fly are found in the US but the most common is Drosophila melanogaster. A small species only about 1/8 inch long, the adults are brown or tan and often have red eyes.
In the US, around 200 species are considered “filth flies”. Among these are the two most common fly pests:
- Houseflies, which are notorious for spreading disease.
- Fruit flies, small but annoying pests that can quickly damage the reputation of a food-related business.
Both houseflies and fruit flies undergo complete metamorphosis. They pass from egg to maggot, pupating and then emerging as adult flies.
Eggs are laid in any moist place that has suitable food for the maggots. Housefly maggots will feed on decomposing organic waste, carrion or manure. The maggots of fruit fly favor ripe or rotting fruit but can survive on most organic waste. The time spent as maggots in either type is controlled by temperature. It can be as short as a few days or as long as several weeks.
Houseflies and fruit flies are normally only active during daytime but they will fly at night in a well-lit area.
Adult flies enter a form of hibernation during the winter to reappear in the spring. Fruit flies can often continue to breed in small numbers throughout the winter due to the heating in most homes.