VARIATION IN EUROPEAN LEPIDOPTERA. 



77 



migrating in search of food ; and on his arrival at the fields in 

 question, they were black with a swarming carpet, waved into ridges 

 here and there where the insects were deeply massed together. This 

 imago is a survival of that vast host, having escaped the starvation 

 which overtook the larger number ; and was caught the following 

 year at the place in question. It corresponds in size, though of not 

 quite so blanched a coloration, with the Alpine var. Merope, whose 

 stunted food-plant and short summer has in lapse of ages affected 

 permanently its size and depth of colour, but not altered the drawing 

 of the pattern. 



Climate has a decided tendency to influence coloration. As we 

 approach the Arctic circle, or ascend to the perpetual snow-line on 

 Alpine summits, we find among the Heterocera that the delineation 

 is accentuated, and the characteristic tones deepened; while, on the 

 contrary, the Rhopalocera suffer in colour and distinctness of marking. 

 Take for instance the moths of Iceland, Finland, and North Russia; 

 look at Cry?nodes Exulis, Pachnobia Alpina, Anarta Melanopa^ and the 

 moths of Shetland, characterised by excess rather than diminution of 

 pattern ; and again the pale blurred Melitcece and other Rhopalocera 

 of the same regions. And I cannot help here referring (when I am 

 speaking of this group) to the remarkable Alpine species, MelitcBa 

 Cynthia. This insect, whose female is extremely similar to that of 

 M. Artemis^ has in the male a considerable area of white, though it 

 retains the general pattern of M. Artemis. I cannot help suspecting 

 that here we have a remarkable and extreme instance of the bleach- 

 ing influence which such climates produce very generally, and on 

 this group of butterflies in especial. 



But on the other hand, as we travel southwards^ we find the 

 colours of the Rhopalocera deepened and enriched : the orange of 

 Melitcea Didyma in Germany becoming fiery red along the Mediter- 

 ranean littoral, and even varying on the northern and southern slopes of 

 the Alps. M. Artemis glows with the warmer tints of var. Frovincialis, 

 Gonepteryx rhamjii is replaced by the orange-flushed Cleopatra^ while 

 their females are undistmguishable, and Anthocharis Cardamines by the 

 vivid Euphenoides of Provence. White becomes replaced by metallic 

 lustre, as in the CcErUonymphidce and in the Anthocharis group. 

 Among the Lyccenidce, too, the ocelli of Z. Lycidas (Trapp), from 

 Switzerland, become illuminated with gold, giving the South European 

 form of Z. Zephyrus (Frivaldsky). Climate, therefore, appears to me 

 to affect colour and pattern merely in intensity, rather than in 

 essential character. 



The influence of food next demands our attention, and I am 

 afraid that I shall differ from many who by their practical experience 



Nov. 1884. E 2 



