194 DARWINISM 



CHAl'. 



two strong arguments against this theory. We have ah-eady 

 seen how generally bright coloration is wanting in desert 

 animals, yet here heat and light are both at a maximum, 

 and if these alone were the agents in the pioduction of 

 colour, desert animals should be the most brilliant. Again, 

 all naturalists Avho have lived in ti'opical regions knoAv that 

 the proportion of bright to dull coloured species is little if 

 any greater there than in the temperate zone, while there arc 

 many tropical groups in which bright colours are almost en- 

 tirely unknown. No part of the world presents so many 

 brilliant birds as South America, yet there are extensive 

 families, containing many hundreds of species, which are as 

 plainly coloured as our average temperate birds. Such are the 

 families of the l)ush-shrikes and ant-thrushes (Formicariid?e), 

 the tyrant-shrikes (Tyrannidte), the American creepers (Den- 

 drocolaptidi^), together with a large proportion of the wood- 

 warblers (Mniotiltida;), the finches, the wrens, and some other 

 groups. In the eastern hemisphere, also, we have the babbling- 

 thrushes (Timaliida?), the cuckoo-shrikes (Campephagidte), the 

 honey-suckers (Meli})hagida'), and several other smaller groups 

 which are certainly not coloured above the average standard 

 of temperate birds. 



Again, there are many families of liirds which spread over 

 the whole world, temperate and tropical, and among these the 

 tro^iical species rarely present any exceptional brilliancy of 

 colour. Such are the thrushes, goatsuckers, haAvks, plovers, 

 and ducks ; and in the last-named group it is the temperate 

 and arctic zones that afford the most brilliant coloration. 



The same general facts are found to prevail among insects. 

 Although tropical insects present some of the most gorgeous 

 coloration in the Avhole realm of nature, yet there are 

 thousands and tens of thousands of species which are as dull 

 coloured as any in our cloudy land. The extensive family of 

 the carnivorous ground-beetles (Carabida3) attains its greatest 

 brilliancy in the temperate zone ; while by far the larger 

 proportion of the great families of the longicorns and the 

 Aveevils, are of obscure colours even in the tropics. In butter- 

 flies, there is undoubtedly a larger proportion of brilliant 

 colour in the tropics ; but if we compare families which are 

 almost equally developed over the globe— as the Pieridae or 



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