184 AKTHROPODA. 



marks the division between the stomach and intestine. It is at 

 this point that the uriniferous tubes join the alimentary canal. 



(e) Behind the intestine the alimentary canal becomes much 

 smaller and is known as the hind intestine or colon. 



(/) Behind the colon, forming the hinder portion of the ali- 

 mentary canal, is the slightly enlarged rectum. The rectum 

 cannot be seen until the ovary is removed, which should be de- 

 ferred until the ducts have been seen. 



Make a drawing showing the position of the parts of the alimen- 

 tary canal in side view. 



Cut the intestine and turn the alimentary canal posteriorly 

 and anteriorly. 



5. Notice the muscles: 



(a) That move the abdominal segments. 



(6) That move the legs (those that supply the wings have 

 been destroyed). 



(c) That move the jaws. 



Do you understand now why the thorax needs to be compar- 

 atively large and firm? 



6. The nervous system is directly comparable to that of the 

 lobster, but the connectives between the ganglia will be found 

 to be distinctly double and the ganglia to be somewhat differently 

 arranged. 1 



The ventral chain will be found to consist of a pair of sub- 

 esophageal, three pairs of thoracic, and five pairs of abdominal 

 ganglia with the connectives between them. Which of these 

 are largest? Why is this the case? Trace the nerves from them 

 and see what organs they supply. 



Trace the connectives forward from the sub-esophageal ganglia 

 and see that they pass around the esophagus, thus forming 

 the circum-esophageal connectives. Cut away the dorsal portion 

 of the head and expose the cerebral ganglia. 



Add the nervous system to the figure that shows the alimentary 

 canal. 



1 The arrangement of the ganglia in insects is very variable, showing 

 mnny gradations in concentration. 



