Flies are insects. There are many types, over a hundred thousand. What is special about flies is that they have two wings instead of four. The most well-known type of fly is the house fly. Some fly species are only a millimeter long, others several centimeters.
Flies lay many small eggs. A larva develops from an egg. This then becomes a new fly.
Flies are only a few days or at most weeks old. They eat small parts of animals or plants, for example, a flake of skin that has fallen on the ground. But flies are also eaten themselves, especially by birds.
What is bad for humans is that flies transmit diseases. After a fly has sat on manure or rubbish, it sometimes flies on our food as well. Some flies bite people or animals such as cows. Finally, there are flies that eat agricultural crops. That’s why a lot of people don’t like flying. It used to be said that flies were the devil’s companions.