ORGANS OF DIGESTION. 59 



INTERNAL ORGANS OF INSECTS. 



HAVING thus taken a brief, but, I trust, an intelli- 

 gible survey of the outside of the body in insects, the 

 student may be supposed to be partly prepared to 

 examine the various organs within the body. It will 

 be convenient, for this purpose, to begin with the 

 organs employed in the digestion of the food, and 

 then pass on to those employed in breathing, sensa- 

 tion, and reproduction. 



t 



ORGANS OF DIGESTION. 



IT is remarkable that the length of the organs 

 of digestion in insects, measuring from the mouth to 

 the vent, is, as in the larger animals, proportioned to 

 the sort of food. Vegetable food, being more crude, 

 or not so like the properties of the animal body, 

 requires more preparation to turn it into nourishment ; 

 and hence, insects, and other animals which feed on 

 vegetables, have their organs of digestion of great 

 length, much longer, indeed, than the body, in which 

 they wind in many folds. Animal food requiring 

 less preparation, the insects which feed on it have 

 their organs of digestion short, and of the same length 

 as the body. In all cases they consist of three layers, 

 the outer membranous, the middle muscular, and the 

 inner mucous. 



