174 ELEMENTS OF COMPARATIVE ZOOLOGY. 



purpose of dissection; pin it out, back uppermost, in the 

 dissecting-pan, in water just deep enough to cover it, and 

 with fine scissors cut away the dorsal wall of the abdomen, 

 taking great pains to remove nothing but the hard parts. 

 In spite of all care the beginner will probably remove the 

 heart a delicate tube lying along the middle of the back 

 with the dorsal wall. Continue the cuts forward, removing 

 the dorsal wall of the thorax. Notice the large muscles which 

 move the wings. If the specimen has been freshly killed, 

 the most striking feature will be a series of silvery-appear- 

 ing air-tubes, tracheae, which connect with the spiracles 

 and ramify all parts of the body. In alcoholic "hoppers" 

 these are distinguishable only with difficulty. Between the 

 body-wall and the viscera will be found the light-colored 

 fat-body. 



In the anterior part of the abdomen, on either side, is 

 a cluster of long oval yellow eggs, and from each mass of 

 eggs a delicate tube (oviduct) may be traced backwards to 

 the region of the ovipositor. Separate the masses of eggs 

 and find, between and below them, the dark-colored ali- 

 mentary canal. Follow this forward and back and make 

 out in it the following parts: In the hinder half of the 

 abdomen the intestine, which in front passes into the much 

 larger stomach. At the junction of the stomach and intes- 

 tine are a number of fine tubes (Malpighian-tubes) which 

 are excretory in function. At the anterior end of the 

 stomach are a number of larger double-cone shaped tubes, 

 the gastric caeca, and in front of these is the large brown 

 crop. The crop is connected with the mouth by a narrow 

 tube, the gullet or oesophagus. 



Remove the alimentary canal by cutting through oesoph- 

 agus (close to the crop) and intestine, and look upon the 

 floor of the abdomen for the nervous system. Can you find 



