LOCUST 179 



Examine the spiracles or stigmata. How many- 

 do you find on each segment? "What is their 

 position? Shape? Note the variations in the 

 last few segments of the body in the two sexes. 

 The females can be distinguished as having the 

 abdomen terminate in four curved prongs. Ex- 

 amine such a specimen. How does the number 

 of sterna differ from the number of terga? In 

 the female the last sternum forms the subgeni- 

 tal plate. Compare it in shape and size with 

 the other sterna. At the posterior end of the 

 subgenital plate is the egg-guide. What is its 

 structure ? Study the structure of the ovipos- 

 itor, which consists of the two pairs of curved 

 appendages already mentioned, together with a 

 third pair lying between the first two. Notice 

 the shape, size, and structure of each pair, their 

 direction of motion, etc. To which segment is 

 each pair attached ? Find lying above the base 

 of the uppermost pair a tergum for which there 

 is no corresponding sternum. At the base of 

 each of these curved appendages is a small plate, 

 the podical plate. Find the opening, the anus, 

 between them. What relation does this bear to 

 the opening of the oviduct ? Just below the pod- 

 ical plates are two other organs, the cerci. To 

 which segment are they attached? Compare 

 these with the parts of the ovipositor. Compare 

 the abdomen of a male with that of the female. 

 How many segments in the entire body ? 

 Draw the abdomen of each as seen from the side and 

 from above. 



Internal Anatomy. — Use, if possible, recently killed 



