DEVELOPMENT OP INSECTS. 



o 



17 



ing parts, and thus are the foundations laid of all the endless 

 diversities which characterize the several species belonging 

 to each tribe and family. 



In the progress of development, we may recognise two 

 principles, which, though apparently opposite to each other, 

 concur and harmonize in their operation: these are expaii- 

 sion and concentration. Thus, while those segments of body 

 which follow the head are greatly enlarged, in order to sup- 

 port the more recently developed organs of progressive mo- 

 tion, they are also more consolidated, and rendered stronger 

 by the union of several pieces which were before separate. 

 The hinder segments, having no such appendages to support, 

 are less dilated, and the whole body is much shortened by 

 the approximation of the segments, which, in this way, com- 

 pose the abdomen, or hinder division of the insect. 



The progress of the metamorphoses of insects is most 

 strikingly displayed in the history of the Lepidopterous, or 

 butterfly and moth tribe.* The egg, which is deposited by 

 the butterfly, gives birth to a caterpillar; an animal, which, 



in outward shape, bears not the slightest resemblance to its 

 parent, or to the form it is itself afterwards to assume. It 

 has, in fact, both the external appearance, and the mechani- 

 cal structure, of a worm. The same elongated cylindric 



* The four periods of the existence of the Bomhyx mor'i, or the moth of 

 the silk-worm, are shown in the annexed cng-raviiigs: Fig-. 145 are tlie ci,-gs; 

 Fig. 146, the Larva, or caterpillar; Fig-. 147, the Pupa, or chr^sidis; and 

 Fig. 148, the I?nagOy or perfect insect. 



Vol. I. 28 



