INSECTS IN GENERAL. 53 



sity of constant reference for the purposes of illustration, to 

 the orders, genera, and species, render the subject improper 

 to be dwelt on here, to say nothing of the imperious obliga- 

 tion of confining this general essay within narrow bounds. 

 We shall, therefore, dismiss all further consideration of the 

 external forms of insects, and proceed to a review of their 

 principal functions. 



We have already insisted on the elevated rank to which 

 insects are entitled in the classification of the living world. 

 Under the relation of animality^ they certainly, as we have 

 said, stand next to the vertebrated animals, being provided 

 with an articulated body, supported by articulated limbs, 

 and being capable of all the various species of motion. Tn 

 proportion to their mass, they exhibit both strength and 

 activity in a most astonishing degree. They are endowed 

 equally with the faculty of perceiving with strength, and at 

 a distance, by means of the organs of the senses, the qualities 

 of bodies, and better, perhaps, than we can appreciate them 

 ourselves. The organs of respiration, in insects, are placed 

 in immediate contact with the fluids, to render them proper 

 for the excitation of life : a circumstance which compensates 

 for the defect of circulation, and probably supplies its place 

 with greater energy, so that the organs of nutrition and 

 generation are not less energetic, nor less perfect, than those 

 of the Crustacea, the annelides, the moUusca, and the zoo- 

 phytes. 



Motions, in insects, though greatly varied, are performed 

 without a correspondent complication of structure. As the 

 parts of their body are, in general, very symmetrical, we find 

 at one side, what is observed at the other, so that the study 

 of one half of their body gives the idea of the correspondent 

 part. In the trunk, the head and its annexes alone are 

 capable of much motion. The three regions of the thorax 

 are all moved by the limbs, without themselves contributing 



