A
window screen (also known as
insect screen,
bug screen,
fly screen,
flyscreen or
flywire) is designed to cover the opening of a
window. It is usually a mesh made of
metal wire,
fiberglass, or other
synthetic fiber and stretched in a
frame of wood or metal. It serves to keep leaves, debris, insects, birds, and other animals from entering a building or a
screened structure such as a porch, without blocking fresh air-flow. Most houses in
Australia, the
United States and
Canada and other parts of the world have screens on the window to prevent entry of flying insects like mosquitoes, fleas, and house flies. Formerly, screens were required to be replaced by glass
storm windows in the winter, especially in regions like the northern United States and Canada, but now combination storm and screen windows are available, which allow glass and screen panels to slide up and down.