SHORTER ARTICLES AND DISCUSSION 



THE INHERITANCE OF SEASONAL POLYMORPHISM 

 IN BUTTERFLIES 



Abe seasonal variations inherited, and may they play a part in 

 evolutionary change? These are questions which Punnett in 

 his recent book on " Mimicry in Butterflies" answers in the neg- 



In no ease are they known to be inherited, and in no ease conse- 

 quently could variation of this nature play any part in evolutionary 



Variations to be of significance in evolution, he tells us, must 

 he "transmissible and independent of climatic and other con- 

 ditions. ' ' 1 



It would seem to require no demonstration that well-estab- 

 lished seasonal variations like those of Araschnia levana-prorsa 

 of Europe in which, it will be remembered, the ground color of 

 the spring brood (levana) is red-brown, that of the summer 

 brood (prorsa) black, are transmissible. Under summer condi- 

 tions in Europe prorsa appears with the regularity of a mono- 

 typic species, true to type. Monotypic species likewise require 

 a certain degree of temperature and amount of moisture to pro- 

 duce their characteristic adult coloration. A. prorsa is by no 

 means peculiar in this respect. It has the definitive adult colora- 

 tion of the species. That which is peculiar is the hereditary 

 rhythmic tendency to swing from prorsa back to levana, which is 

 so strong that experimental control can not wholly cope with it. 

 Summer conditions artificially prolonged result in the appear- 

 ance of some prorsa in prorsa' 's immediate offspring, but some- 

 times the intermediate, ponma, is the outcome. A far larger 

 number of individuals of the lot under experimentation, how- 

 ever, refuse to be forced out of the chrysalis by artificial heat, 

 hibernate, and become levana. These color variations, therefore, 

 are not subject wholly to the environment, nor wholly to 

 heredity. 



A common hereditary basis evidently underlies both of the 



i Pp. 131, 132. 



310 



