The butterfly's life cycle consists of four stages, from egg, larva, pupa, to an adult. In the adult stage the butterfly can live from a week up to a year, depending upon the species. Their eggs are generally laid on plants, the egg stage lasting a few weeks. The eggs consisting of a hardened shell, which is lined with a thin waxed coating that prevents it from drying out before the larva has time to develop. The eggs are stuck to a plant with glue. The larvae, or as we generally refer to them, the caterpillars, consume plant leaves. They mature through a period of stages, at the end of each stage the larva sheds its outer layer and expands a new layer. It begins to develop butterfly wings, during the last larval stage. When the larva becomes fully grown it morphs into the pupa stage. The pupa then goes through a metamorphosis transforming itself into a fully developed butterfly. The butterfly's diet consists primarily of nectar, but they also derive nourishment from pollen, tree sap, and rotting fruits, etc... They are important to nature in that they help spread pollen. Some butterflies such as the Monarch are migratory and travel long distances. Their main characteristic being the large, brightly colored wings, which flutter when in flight.