cxxvu 



From the examples mentioned we must not draw the con- 

 clusion that local forms always exhibit some conspicuous 

 distinction. On the contrary, a large proportion are but 

 slightly different, or their differences are inconstant. Our 

 knowledge of this side of the variation of British Lepidoptera 

 is still far from being complete. It will require a great deal 

 more collecting and patient study before we have a satis- 

 factory survey of the variation of the Lepidoptera within the 

 British Isles, and particularly before the differences between 

 our insular fauna and that of the Continent can be clearly 

 demonstrated in all its aspects. Here is a field for the younger 

 Entomologists, and I should recommend the thorough study of 

 a few species throughout the British Islands and at least 

 Western and Central Europe as a task well within the capacity 

 of any enthusiast. The results of such research, for instance 

 upon species like Pieris napi and some of the commoner 

 Satyrinae, would be most valuable, especially if the distinc- 

 tions observed were tested by experiments in breeding. 



Among the Continental Lepidoptera the species of which 

 the geographical variation has attracted most attention in 

 recent years, is Parnassius apollo, which extends from the 

 Sierra Nevada in the south of Spain over the mountainous 

 countries of Central Europe southward to Sicily and eastward 

 to Central Asia, reappearing in the north in the Baltic countries. 

 The local races described of P. apollo are now almost innu- 

 merable. The species varies so much locally that every 

 mountain stock and every isolated range has its own race, 

 some easily distinguished, others overlapping in characters, 

 and others evidently bearing a different name because they 

 are from another valley. I will not multiply the illustrations 

 of geographical variation in European Lepidoptera, many of 

 you knowing as much about it as I do, or more, but will 

 proceed to show some examples from the tropics. 



As you know, the phenomenon of geographical variation was 

 first clearly perceived and stated by Bates. The observations 

 upon which this explorer based his opinion were made in the 

 tropics, and scientists at home were long under the impression 

 that this kind of modification of a species in different districts 

 obtained in tropical countries rather than in the temperate 



