INSECTS IN GENERAL. 85 



the observer can either accelerate or retard this operation, so 

 as to see it performed at will under his immediate inspection, 

 in the duration of a minute. Interestincf, however, as this 

 subject is, we must dismiss it for the present, reserving any 

 minuter details thereon for the supplements to the separate 

 orders of this class. 



A subject of perhaps not less interest is the determination 

 of the climates which are proper to the different races of in- 

 sects, or, in other words, their geographical distribution. 

 Such distribution is in close relation with the nutrition of 

 these animals ; for since the Author of Nature has extended 

 living beings over every point of the surface of the globe, 

 capable of sustaining them, and since these beings vary with 

 climate, it must happen that the alimentary substances by 

 which they are sustained, must also differ according to the 

 places in which they pass their lives, and be subjected, like 

 the animals themselves, to the same geographical circum- 

 scription. 



Independently of this consideration, the temperature which 

 is suitable to the development of one species, is not always 

 equally proper for that of another. Thus the extent of the 

 covmtries occupied by certain species, has its necessary limits, 

 beyond which they cannot pass, at least suddenly, without 

 ceasing to exist. 



Another consequence follows from these principles : where 

 the empire of Flora ends, there likewise terminates the do- 

 main of Zoology. The animals which feed on vegetables, 

 could not exist in regions of complete sterility, and those 

 which are carnivorous would be equally deprived of their 

 prey. 



From observation we find that the countries most abound- 

 ing in animals with articulated feet, and especially in in- 

 sects, are those whose vegetation is the richest and the most 

 speedily renewed. Such are the effects of a powerful and 



