Scarce merveille du jour moth  (Moma alpium)

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. (1984) Colour Identification Guide to Moths of the British Isles. Viking Press, London.
   
3. South, R. (1961) The moths of the British Isles. Frederick Warne & Co. Ltd., London.