cxxvm 



zone. That was a misconception, but an excusable one. 

 In the tropics there are so many more brightly coloured and 

 large species than in the temperate countries, and the differ- 

 ences in large and gaily coloured specimens appear so much 

 more pronounced for our eyes than those obtaining in small 

 and sombre-coloured species that, with this reservation, the 

 tropical species may be said to exhibit the various kinds 

 of variation in a more intense form, but the geographical 

 variation is just as regular a phenomenon in the temperate 

 zones as in the tropics. The classical countries where Bates 

 and Wallace made their discoveries are the Amazons and 

 the Malay Archipelago. Considering the continuity of the 

 Amazon basin from the Andes to the Atlantic, and the slight 

 rise in height from sea-level at Para to little over 300 ft. at the 

 foot of the Andes, a distance of nearly 2000 miles. Bates must 

 have been fairly startled by the modifications within the 

 species collected by him at Para on the Lower Amazons, 

 Obidos and Manaos on the Middle Amazons, and Ega on the 

 Upper Amazons. We take it now as a matter of course that 

 we receive different species or different geographical races from 

 these three Amazonian districts. After a fact of this kind has 

 been clearly pointed out, it is easy to follow the lead and apply 

 that knowledge also elsewhere. The geographical variation 

 discovered by Bates on the Amazons We now know to obtain 

 in a no less marked degree on both American continents in the 

 direction from east to west as well as from north to south. A 

 tropical species which has spread north and south into the 

 temperate countries is usually represented by a different 

 geographical race in the east of the U.S.A. and in the Western 

 States, in East Mexico and in West Mexico, the eastern Mexican 

 race extending as a rule south into Honduras and even 

 Nicaragua, another race again in Costa Rica and Panama, 

 West, Central, and East Colombia, and so on. 



Experience has taught us that in Africa, south of the Sahara, 

 the chief faunistic provinces as regards Lepidoptera are like- 

 wise well marked. Without going into detail I mention that 

 the West African forest region has two major provinces, the 

 one extending from Senegambia to the Niger, and the second 

 from the Niger to the Congo basin ; South Africa has generally 



