162 TROPICAL NATURE, AND OTHER ESSAYS. 



for the great number of brilliant birds, insects, and 

 flowers, which are found between the tropics. 



But before proceeding to discuss this supposed ex- 

 planation of the colours of living things we must ask the 

 preliminary question, whether it is really the fact that 

 colour is more developed in tropical than in temperate 

 climates, in proportion to the whole number of species ; 

 and even if we find this to be so, we have to inquire 

 whether there are not so many and such striking ex- 

 ceptions to the rule, as to indicate some other causes at 

 work than the direct influence of solar light and heat. 

 As this is a most important branch of the inquiry, we 

 must go into it somewhat fully. 



It is undoubtedly the case that there are an immensely 

 greater number of richly-coloured birds and insects in 

 tropical than in temperate and cold countries, but it is 

 by no means so certain that the proportion of coloured 

 to obscure species is much or any greater. Naturalists 

 and collectors well know that the majority of tropical 

 birds are dull-coloured ; and there are whole families, 

 comprising hundreds of species, not one of which ex- 

 hibits a particle of bright colour. Such are, for example, 

 the Timaliidae, or babbling thrushes of the Eastern, 

 and the Dendrocolaptidae, or tree-creepers of the Western 

 hemispheres. Again, many groups of birds, which are 

 universally distributed, are no more adorned with colour 

 in the tropical than in the temperate zones ; such are the 

 thrushes, wrens, goatsuckers, hawks, grouse, plovers, and 

 snipe ; and if tropical light and heat have any direct 

 colouring effect, it is certainly most extraordinary that 

 in groups so varied in form, structure, and habits as 

 those just mentioned, the tropical should be in no wise 



