At different times considerable attention has been paid to the general darkening in colour of our British insects, compared with Centrall European and with American forms. In Britian, many species become much darker(some absolutely black) on various parts of the West Coasts of Ireland and Great Britian, and, as a general rule, the more humid districts produce the darker specimens, e.g. Acronycta (Viminia) euphorbiœ var. myricœ, Xylophasia polyodon vars. infuscata and nigra, Viminia rumicis var. salicis, etc.