My dear M^r. Darwin,

What you have sketched above seems to me to be quite in accordance with the few facts on the subject which we possess.¹ I am struck with the idea of two apparently adverse tendencies at work among Moths, one tending to intensify any splendour of colour in view of sexual selection, and the other to conceal it from attracting the notice of enemies. The double end seems to be attained in those numerous species whose brightly-coloured hindwings are covered by the dull forewings when the creature is dormant or at rest, but can readily be displayed on occasion. The dull underside of many Butterflies in conjunction with a brilliant upperside seems to afford similar evidence.

Always faithfully yours, | Roland Trimen