Taxonomically the butterflies belong to the insects. Insects develop from egg to adult in three different ways. Butterflies are holometabolic insects that have a complete change of form, or metamorphosis, between the immature form and the adult. This means that the larva that hatches from the egg, in this case the caterpillar, in no way resembles the adult, the butterfly, either in appearance or in behaviour and further way of life. Metamorphosis takes place in the chrysalis, or pupa. The number of generations, or broods, a butterfly species has in a year varies. Most species have just one, others two or three. There are a few species with a two-year development, the caterpillar or chrysalis living longer than a year and hibernating twice. These species, such as some ringlets (Erebia spp.) occur where food is scarce, in mountainous areas with short summers.