Netted carpet moth  (Eustroma reticulatum)

Pupation: the process of becoming a pupa, the stage of 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 (Dec 2002):
   http://www.ukbap.org.uk
   
2. Skinner, B. (1984) Colour Identification Guide to Moths of the British Isles. Viking Press, London.
   
3. Carter, D.J. and Hargreaves, B. (1986) A field guide to caterpillars of butterflies and moths in Britain and Europe. Collins, London.
   
4. Hooson, John. National Trust. Pers. comm.