Why do flys have no energy in winter?

This is a misconception. Flies do not lose their energy in the winter. While some flies may become less active during the colder months, they do not run out of energy or die because of it.

Flies are cold-blooded animals, meaning their body temperature is regulated by the environment. When the temperature drops in the winter, flies become less active because their metabolism slows down. This means they don't need to eat as much or move as much. However, they do not run out of energy entirely and can still fly and survive in cold weather.

Some fly species have adaptations that help them survive the winter. For example, some flies produce a chemical called glycerol, which acts as an antifreeze and prevents their body fluids from freezing. Others may seek shelter in warm places or enter a state of dormancy called diapause, where their development and metabolism are temporarily suspended.

In summary, flies do not lose their energy or die in the winter. They may become less active due to the cold weather, but they can still fly and survive using various adaptations.