On the Seasonal Dimorphism of Butterflies. 103 



The question now arises, how far does the 

 transforming influence of climate extend ? When 

 a species has become transformed by climatic 

 change to such an extent that its new form pos- 

 sesses the systematic value of a new species, does 

 it return to its older form by removal to the old 

 climatic conditions ? or would it under these cir- 

 cumstances become again transformed in a new 

 manner ? This question is not without impor- 

 tance, inasmuch as in the first case climatic 

 influences would be of little value in the forma- 

 tion of species, and there would result at most 

 only a fluctuation between two extremes. In the 

 same manner as in seasonally dimorphic species 

 the summer and winter forms now alternate with 

 each other every year, so would the forms pro- 

 duced by warmth and cold then alternate in the 

 greater periods of the earth's history. Other 

 groups of animals are certainly changed by the 

 action of different climatic influences ; but in but- 



the scent-tufts in the sphinx-moths is shown in Proc. Entom. Soc. 

 1878, p. ii. Many British moths, such as Phlogophora meticu- 

 fasa, Cosmia trapezina, &c. &c., have tufts in a similar position. 

 The fans on the feet of Addalia bisetata, Herminia barbalis, 

 H. tarsipennalts, &c., are also probably scent organs. A large 

 moth from Jamaica, well known to possess a powerful odour 

 when alive (Erebus odorus Linn.), has great scent-tufts on the 

 hind legs. For the application of the theory of sexual selection 

 to butterflies, see, in addition, to Darwin's "Descent of 

 Man," Fritz Miiller in " Kosmos," vol. ii. p. 42 ; also for 

 January, 1879, p. 285; and Darwin in "Nature," vol. xxi. 

 January 8th, 1880, p. 237. R.M.] 



