194 
DARWINISM 
CHAP. 
two strong arguments against this theory. We have already 
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 production of 
colour, desert animals should be the most brilliant. Again, 
all naturalists who have lived in tropical regions know that 
the proportion of bright to dull coloured species is little if 
any greater there than in the temperate zone, while there are 
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 avei’age temperate birds. Such are the 
families of the bush-shrikes and ant-thrushes (Formicariidae), 
the tyrant-shrikes (Tyrannidse), the American creepers (Den- 
drocolaptidae), together with a large proportion of the wood- 
warblers (Mniotiltidae), the finches, the wrens, and some other 
groups. In the eastern hemisphere, also, we have the babbling- 
thrushes (Timaliidse), the cuckoo-shrikes (Campephagidse), the 
honey-suckers (Meliphagidse), and several other smaller groups 
which are certainly not coloured above the average standard 
of temperate birds. 
Again, there are many families of birds which spread over 
the whole world, temperate and tropical, and among these the 
tropical species rarely present any exceptional brilliancy of 
colour. Such are the thrushes, goatsuckers, hawks, 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 whole 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 (Carabidae) attains its greatest 
brilliancy in the temperate zone; while by far the larger 
proportion of the great families of the longicorns and the 
weevils, 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 
