On the Seasonal Dimorphism of Butterflies. 7 



white in winter and of a grey-brown in summer, 

 both colours of the species being evidently of 

 important use. 



It might be imagined that analogous phenomena 

 occur in butterflies, with the difference that the 

 change of colour, instead of taking place in the 

 same brood, alternates in different broods. 6 The 

 nature of the difference which occurs in seasonal 

 dimorphism, however, decidedly excludes this view ; 

 and moreover, the environment of butterflies 

 presents such similar features, whether they emerge 

 in spring or in summer, that all notions that we 

 may be dealing with adaptational colours must be 

 entirely abandoned. 



I have elsewhere 7 endeavoured to show that 

 butterflies in general are not coloured protectively 

 during flight, for the double reason that the colour 



guising colours of species which, like the Alpine hare, stoat, 

 and ptarmigan, undergo seasonal variation of colour. See a 

 paper " On the Disguises of Nature, being an inquiry into the 

 laws which regulate external form and colour in plants and 

 animals." Edinb. New Phil. Journ., Jan. 1860. In 1873 I 

 attempted to show that these and other cases of " variable 

 protective colouring " could be fairly attributed to natural selec- 

 tion. See Proc. Zoo. Soc., Feb. 4th, 1873, pp. 153 162. R.M.] 



e [A phenomenon somewhat analogous to seasonal change 

 of protecting colour does occur in some Lepidoptera, only the 

 change, instead of occurring in the same individual, is dis- 

 played by the successive individuals of the same brood. See 

 Dr. Wallace on Bombyx Cynthia, Trans. Ent. Soc. Vol. v. 

 p. 485. R.M.] 



7 " Uber den Einfluss der Isolirung auf die Artbildung." 

 Leipzig, 1872, pp. 5562. 



