THE LOCUST, OR GRASSHOPPER 53 



Does it extend outside of the abdomen ? It will take care- 

 ful dissection to find the heart and not injure it. Often it 

 may be seen best by dissecting the abdomen from the 

 ventral side. Now cut along the right of the median line, 

 parallel. with the first slit, and lift away the skin from the 

 roof of the abdomen. 



Note the white, silvery air tubes (trachece) (page 161 of 

 the text) ramifying throughout the body. Note the large 

 longitudinal tracheae running along the sides of the abdo- 

 men. How are these connected with the spiracles? 



Make a diagram of the tracheal system showing the con- 

 nection with the spiracles. 



Mount some of the trachea? under a microscope and note 

 their appearance. A spiral elastic fiber is coiled inside the 

 wall of each tube to hold it open. 



Make a drawing of a piece of a trachea. 



There are usually two masses of yellowish, cylindrical 

 eggs in the abdomen of the female. The eggs are piled 

 in tiers on the sides and top of the alimentary canal. Note 

 a white tube, the oviduct, running posteriorly from each egg 

 mass to the ventral side of the abdomen. Here the two 

 oviducts unite and form a tube, the vagina, which opens to 

 the outside between the ovipositors. 



Remove the egg masses and note the long, straight ali- 

 mentary canal, running from the head to the posterior end 

 of the body. Begin at the mouth and trace it, noting the 

 following parts : 



The esophagus, or gullet, which runs from the mouth 

 upward through the head and then posteriorly into the 

 thorax. 



In the thorax the esophagus enlarges into a large food 

 reservoir, the crop, in which the food is held for a time 



