292 ELEMENTARY ENTOMOLOGY 



membrane. Leading from the testes are two very fine, hairlike 

 tubes known as the vas deferens. These pass down to the ventral 

 side of the body on either side of the alimentary tract and unite, 

 forming the ejaculatory duct, which opens dorsally to the subgenital 

 plate. Just before the union of the vas deferens they are joined 

 on either side by a number of fine tubules known as the seminal 

 vesicles, the function of which is to store up the products of the 

 reproductive glands. 



Exercise 36. Make a careful drawing of the side view of a locust, showing 

 the alimentary tract, accessory organs of digestion, and either the male or the 

 female reproductive system. 



4. Nervous system. With a pair of fine scissors cut the alimen- 

 tary tract through the esophagus and small intestine, and carefully 

 remove, together with the reproductive organs. Great care must be 

 taken to not injure or displace any of the other organs. Also care- 

 fully remove the right side of the chitinous portion of the head. 



The nervous system consists principally of a supra-esophageal 

 ganglion, or brain, which lies dorsal to the esophagus. This is a large, 

 whitish mass of nervous tissue and, if carefully dissected, can be 

 seen to be directly connected with the compound eyes. Running 

 on either side of the esophagus is a small, white nerve cord that 

 unites on the ventral side, forming the sub-esophageal ganglion. 

 Running from this ganglion toward the posterior end of the body 

 is the ventral nerve cord. If carefully examined, this will be found 

 to consist of two parallel white cords that are occasionally united 

 by the ventral ganglia, from which arise numerous lateral nerves. 

 These ventral ganglia occur in the following segments, the 

 prothorax, mesothorax, metathorax, and abdominal segments two, 

 three, five, six, and seven. 



5. Muscular system. In elementary work of this sort no attempt 

 will be made to trace out the different sets of muscles, but the 

 general relation of the different muscles to the segments should be 

 noted. In the mesothorax and metathorax notice the large wing mus- 

 cles ; also in the abdomen notice the longitudinal and ventral bands. 



6. Respiratory system. The respiratory system is made up of 

 tubes known as tracheae. These open out along each side of the 

 body ; the openings, which have already been noted, are termed the 



