Large white  (Pieris brassicae)

Hibernation: a winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer. In insects, the correct term for hibernation is 'diapause', a temporary pause in development and growth. Any stage of the lifecycle (eggs, larvae, pupae or adults) may enter diapause, which is typically associated with winter.
Pupa: stage in an insect's development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis. The pupa is often covered by a silk cocoon.

1. Carter, D. (1992) Butterflies and moths. Dorling Kindersley, London.
   
2. Asher, J., Warren, M., Fox, R., Harding, P., Jeffcoate, G. & Jeffcoate, S. (2001) The Millennium Atlas of Butterflies in Britain and Ireland. Oxford University Press, Oxford.
   
3. Carter, D. & Hargreaves, B. (1986) A field guide to caterpillars of butterflies and moths in Britain and Europe. William Collins & Sons Ltd, London.