Sword-grass moth  (Xylena exsoleta)

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.
Larval : of the stage in an animal's lifecycle after it hatches from the egg. Larvae are typically very different in appearance to adults; they are able to feed and move around but usually are unable to reproduce.
Pupal stage: 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.
Single-brooded : (also known as 'univoltine'). Insect life cycle that takes 12 months to be complete, and involves a single generation. The egg, larva, pupa or adult over winters as a dormant stage.

1. UK BAP Species Action Plan (December 2001):
   http://www.ukbap.org.uk
   
2. Skinner, B. (1884) Moths of the British Isles. Penguin Books, Harmondsworth.
   
3. South, R. (1961) Moths of the British Isles. Frederick Warne and Co. Ltd, London.
   
4. Carter, D.J. and Hargreaves, B. (1986) A field guide to caterpillars of butterflies and moths. William Collins and Sons, London.
   
5. Pers. observation from images.
   
6. Marren, P. (1998) The English Names of Moths. British Wildlife, 10: 29-38.
   
7. Leverton, R. (2001) Enjoying Moths. Poyser, London.