46 



as temporarily applied (in an unusual degree), or 

 through the accidental transportation of the insect into 

 a naturally warmer atmosphere. 



§ III. Nature of the country and of the soil. 



Before we proceed to inquire to what extent the out- 

 ward aspect of insects is liable to be controlled by the 

 physical state of the areas in which they severally 

 obtain, it may not be altogether out of place to offer a 

 few reflections on the superiority which some regions 

 possess intrinsically over others, both for the increase 

 and diffusion of the animal tribes. To suppose that aU 

 countries within the same parallels of latitude are 

 equally favourable for the development of life (not to 

 mention the after-dispersion of it), is contrary to experi- 

 ence ; for although (as we have already pointed out) the 

 organic world does certainly, when viewed in the mass, 

 approach its maximum as we near the tropics, there are 

 at the same time so many violations of this law, that we 

 cannot admit its operation except in a broad and general 

 sense. 



In a former section of this chapter, I drew attention 

 to the fact, that certain islands, equatorial and subaustral, 

 are anything but suggestive of their actual positions 

 with respect to the line of central heat on the surface of 

 the earth. It was with regard to climate alone, however, 

 that I wished them to be imderstood: and it is not 

 until now that I have ventured to urge the necessity of 



