JOURNAL OF VARIATION. 
No. 7. VoL. II. September 1st, 1891. 
MELANISM AND MELANOCHROISM IN 
BRITISH LEPIDOPTERA. 
By J. W. TUTT, F.E.S. 
{Concluded from page g8.) 
MUST say that, ingenious as this theory is, the 
following explanation by Dr. Chapman appeals 
much more strongly to me. It shows how com- 
pletely Dr. Chapman has grasped the subject. 
As is usual with his writing, it is so clear that any 
addition to or subtraction from the original would do harm 
instead of good. He writes: — ‘‘I have no doubt my theory 
{Ent. Mo. Mag., vol. xxv., p. 40) is correct in a large number 
of cases, but as to the ground which it actually covers, I have 
not made observations enough to make even a guess. Mr. 
Merrifield finds that delay in the larval (or pupal ?) stage pro- 
duces darker specimens^ — cold and wet produce such delay. 
It occurs to me to inquire whether there is any correlation 
between these facts. That is, dark coloration is advantageous 
to a species when living in a damp and cold climate, and will 
therefore no doubt prevail by ‘ natural selection.’ Will the 
individuals of a species, that is, or has been i 
so circumstanced, acquire a habit of re- ^ 
spending immediately in coloration to any 
change in the special climatic circumstances ^ 
in which it is placed ? A species varies, say, ^ 
in colour. Let us arrange it in diagram- ^ 
matic form accordingly : — Diag. 1. 
“Then in a wet season batch No. 5 (owing to its darker 
^ To wit, the early broods of Tephrosia crepusculaHa, Selenia illustriria, S. 
illunaria and Pier is napi. — ^J.W.T. 
