Butterflies are a chiefly diurnal group of the order Lepidoptera (which also includes moths). Adults have large, often brightly coloured wings, and conspicuous, fluttering flight. The group comprise the true butterflies (superfamily Papilionoidea), the skippers (superfamily Hesperioidea) and the moth-butterflies (superfamily Hedyloidea). All the many other families within the Lepidoptera are referred to as moths. The earliest known butterfly fossils date to the mid Eocene epoch, 40–50 million years ago.