Flies have only one pair of wings, unlike all other insects which have two. Crane flies, gnats and mosquitoes are all kinds of fly. Flies have mouthparts that suck or lap up food. Some kinds have piercing mandibles (jaws). We often see flies as a nuisance because they spread diseases. But they are essential to the process of decomposing dead animals and plants, and waste. Many kinds also spread pollen, or are food for other animals.

Maggots

Most flies lay eggs (some kinds give birth to live young). Egg-laying flies lay them in places that will supply their young with plenty of food. These may include a dead animal or rotting vegetation. They hatch into larvae, called maggots, after a few days. Using their biting mouthparts, they eat constantly for about a week. They then find a sheltered place to pupate. After two days, they emerge from their pupae as adult flies.

Sticky feet

Flies can walk upside down on ceilings. They can do this thanks to the sticky hairs on the pads of their feet. To stop them getting permanently stuck upside down, each foot also has a pair of claws. These help them push their sticky feet off the ceiling when they need to fly away.

Tsetse fly

The tiny tsetse fly, only 5 millimetres long, is a serious pest. The long mouthpart, which has “teeth” at its tip, is used to pierce the skin of animals and suck up its blood. The tsetse fly can pass on fatal sleeping sickness to cattle and humans.