40 



AN ECONOMIC ENTOMOLOGY. 



which are primarily sent out to the organs and appendages lying 

 within that particular segment. In adults there is a tendency 

 to a union of the thoracic ganglia, and in the abdomen two are 

 usually confluent toward the anal end of the body. The digestive 



system is usually in- 

 FiG. 21. nervated by a spe- 



cial ganglion, and 

 has its own, partly 

 distinct system. In 

 the higher insects the 

 thoracic ganglion is 

 the most important 

 in the body for the 

 life of the insect, and 

 if this be cut or 

 destroyed the insect 

 dies at once. Any 

 other ganglion may 

 be cut without pro- 

 ^ ducing immediate 



death, and the brain. 



Nervous system of the honev bee at a, and of its . 



larva at b. usmg that term for 



the ganglion con- 

 tained in the head, may be entirely removed without necessarily 

 killing the insect itself. 



While, as stated, the nervous system is well developed and all 

 the organs are well furnished with nerve endings, yet it is prob- 

 able that insects are not particularly sensitive. The oft- cited 

 case of the butterfly that was captured and pinned while alive, 

 then escaped from the collector, and returned at once to its 

 feeding among the flowers without apparent inconvenience, is 

 known to most readers. If a dragon-fly be captured and held 

 by the wings loosely, so as to prevent its escape but not to 

 injure it, and the tip of its abdomen is then presented to its 

 mouth, it proceeds at once to eat it as far as it can reach, with- 

 out any apparent knowledge of what it is doing. It will thus 

 devour, with the greatest portion of the abdomen, half its diges- 

 tive system, nearly half its entire nervous system, and a large 

 part of its heart ; yet, if it be then released, it will fly off", little 



