272 THiS ENTOMOLOGIST. 



In North America, but chiejEly on the western side of that 

 Continent, several species are said to have been found. Of these 

 Machaon, Antiopa, Atalanta, and Phlcsas seem certainly to occur, 

 while Hyale, Edusa, Rhamni, Comma, Sylvanus, and Thaumas have 

 all been reported, and if they do not actually occur are represented 

 by species very closely allied, as are C-album, Aglaia, and 

 Argiolus. A supposed variety of Ruhi has been found in Cali- 

 fornia, and Rap(B has been introduced into Canada, &c., in late 

 years, and seems already to have developed a climatic race. 



Finally, Cardui appears to occur nearly all over the world, 

 except in South America. 



Of the species mentioned above, twenty-one have been found 

 within or near the arctic circle, namely, Machaon, Cardamines, 

 Napi, Antiopa, Urticcs, Athalia, Selene, Euphrosyne, Aglaia, 

 Lathonia, Tithonus, Pampthilus, Typhon, Semiargus, Icarus, 

 Astrarche, ^gon, Phlcsas, Ruhi, Malvee, and Comma. 



If we are to judge, therefore, from the wide distribution, we 

 must place Cardui at the head of the list. It must be kept in 

 mind, however, that this butterfly is a strong flyer, and of a 

 roving disposition, and may have extended its area in compara- 

 tively recent times. On the other hand, it evidently belongs to a 

 very ancient family, and the probabilities are in favour of its 

 early existence. 



Next in age to Cardui, even if not surpassing it, I am inclined 

 to put Hyale, on account of its occurrence in South Africa. 

 This is not the only European insect that inhabits that region, 

 and it seems incredible that they should have all got there by 

 migration across Africa in its present condition. In fact, their 

 presence alone would suggest the probability of a more temperate 

 climate having once prevailed in tropical Africa, but we have 

 other and stronger evidence that sucli was really the case during 

 the Glacial Period. When intense cold, with extensive ice-sheets 

 and snow-fields, covered the greater part of Europe, the meteoro- 

 logical conditions of the African Continent must have been 

 materially affected, and the greater part of the European 

 temperate fauna and flora must have been driven to take refuge on 

 the south side of the Mediterranean, which was then bridged, as 

 it were, by several land connections between Europe and Africa. 

 That many of the refugees penetrated far to the south there is 

 evidence to show, from the species of arctic plants that still 



