Dear Sir,

The Ghost Moth.

On thinking over the fact mentioned at page 402 in the first volume of “The Descent of Man”, that “in the Shetland Islands males (of H. humuli) are frequently found which closely resemble the females”¹—which fact I can corroborate, as I have seen male specimens thus varied in collections made at Peterhead²—it occurs to me that this smaller variation in the case of the male moth may arise as follows: The twilight in those northern regions at the season of the year when H. humuli abounds is so different from our southern twilight that one might say there is no dusk in the north at that time; and thus the mode of sexual selection which I supposed to influence the appearance of the male moth in my letter to you of yesterday would not come into operation there.— But would not this be in truth a confirmation of the theory I ventured to lay before you?—³

Yours most respectfully | George Fraser