A butterfly is a mainly day-flying insect. The butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured wings, and conspicuous, fluttering flight. Butterflies comprise the true butterflies, the skippers and the moth-butterflies. The earliest known butterfly fossils date to the mid Eocene epoch, between 40-50 million years ago. It is a popular belief that butterflies have very short life spans. However, butterflies in their adult stage can live from a week to nearly a year depending on the species. Many species have long larval life stages while others can remain dormant in their pupal or egg stages and thereby survive winters.