SO LABORATORY WORK. 



INTERNAL STRUCTURE. 



The internal structure of the grasshopper in its larger 

 features is readily made out. Select a large female for the 

 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- 

 appearing 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 c&ca, and in front of these is the large brown 



