GRASSHOPPER: LABORATORY WORK. 



Can you distinguish three regions head, thorax, and 

 abdomen in the body ? Where would you draw the lines 

 between these regions ? and why at these points ? 



Notice that the abdomen is made up of a series of rings 

 (segments or somites) essentially like each other. Exam- 

 ine a ring at about the middle of the abdomen, and see that 

 it is made up of dorsal and ventral hardened halves, united 

 by a more flexible membranous portion. Look at the side 

 of the somite and find a small opening (spiracle). How 

 many somites bear similar spiracles ? Has any somite more 

 than a pair of spiracles ? Could you speak of these spiracles 

 as being segmentally arranged ? 



Examine the base of the abdomen and see that its first 

 segment is incomplete. Look at the lower surface and see 

 if you can find the lower half of this ring. On the sides of 

 this first ring notice a large oval thin spot (tympanic mem- 

 brane), the so-called ear. Can you find a spiracle near 

 the ear ? 



The tip of the abdomen varies in shape in the two sexes. 

 In the female it is provided with two pairs of pointed out- 

 growths (ovipositor). The male lacks these, and the tip is 

 rounded and frequently upturned. Study this region care- 

 fully in each sex, making out the following points : 



In the male notice that the ventral halves of the terminal 

 segments are much larger than the dorsal portions. (This 

 overgrowth is called hypertrophy.) Counting from the 

 base, how many rings can you find in the whole abdomen ? 



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