MELANIC VARIATION IN LEPIDOPTERA. 1 23 



We all know how rapidly the pairing of our Lepidoptera is 

 effected. Edwards gives instances of freshly developed males 

 gathering round a female pupa to await the emergence of the 

 perfect insect, and the method adopted by many collectors of 

 attracting males by the exposure of a newly emerged female is 

 usually productive of a series of the finest specimens. 



I have myself observed in the case oiAcidalia rubricata on 

 a warm evening in August, the extreme rapidity with which the 

 males appear to be developed, and how immediately they hurry 

 to pay their attentions to the scarcer and less active females 

 which cling to the grasses and occasionally rise to meet them 

 in their flight. I can scarcely imagine a colour better suited 

 for rapid absorption of heat, with the exception of black, than 

 the beautiful dark red of fresh specimens of this insect, unless 

 it be perhaps the brilliant green of the under side of Thecla ruM. 

 Applying this to the more or less melanic varieties of high lati- 

 tudes, I think we have a sufficient explanation of the process 

 of selection by which these varieties are established and con- 

 tinued under the influence of a climate essentially unfavourable 

 to the paler forms. Those males whose colour enabled them 

 to absorb the heat most rapidly would naturally be the first to 

 harden their wings and to acquire a degree of vitality sufficient 

 to enable them to commence their flight. If we imagine the 

 emergence of a pale and a dark variety side by side at the same 

 moment, it is more than probable that the paler specimen 

 would remain inactive among the herbage, when his darker 

 companion had already commenced his flight. In unfavourable 

 weather the degree of warmth sufficient to arouse even the 

 darkest varieties might be of very short duration, and if this 

 were so the less favoured males might be wholly deprived of the 

 degree of energy necessary to enable them to find their females. 

 The shorter the continuance of passing gleams of sunshine, the 

 greater would be the influences brought to bear against them ; 

 and each separate instance, however unfrequent such instances 



