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A.NJD ~f^ 



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 

 so circumstanced, acquire a habit of re- 

 sponding 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 



1 To wit, the early broods of Tephrosia crepiiscularia, Sdenia ilhistrxria, S, 

 illunaria and Pieris itapt. — J.W.T. 



