INTRODTJCTION. XXI 



we see by this, that a wing is supported in its 

 flight like a sail by its cordage." 



The Abdomen. — This is the third division of 

 the insect ; it is composed of rings, which vary in 

 number from one to fifteen : most of these rings 

 have an open pore placed laterally ; these are the 

 breathing holes through which the fluids of the 

 animal become aerated ; they are termed stigmata. 

 In some, the last ring contains the anus, or vent, 

 and the organs of generation ; in some, it includes 

 either the means of defence of the insect, such as 

 a sting, or instruments which are subservient to its 

 instincts, as saws, ovipositors, pincers, &c. 



The Organs of Digestion. — These consist of a 

 gullet, one or more stomachs, and an intestinal 

 canal, into which numerous fine vessels secrete a 

 fluid analogous to saliva and to bile. 



In the higher animals, the steps by which the 

 raw food is assimilated to the body can be made 

 out. We know that the secretions result from 

 glands and minute arteries, and that absorbents take 

 up that which is prepared in the great reservoirs of 

 life, the stomach and intestines, to pour it into the 

 veins, and thence into the heart. The circle is 

 clearly traceable by reasoning and by sense ; but 

 insects have no true circulating nor absorbent sys- 

 tem ; and yet they secrete fluids which not only 

 serve for digestion, but for defence. The ant dis- 

 gorges an acid ; the bee elaborates a poison ; the 

 glow-worm an unctuous fluid, which, becoming 



