26 



ANIMAL BIOLOGY 



2. Secure an active grasshopper, put it in a live cage, 



and watch the movements of the upper and 

 lower halves of the abdominal segments. De- 

 scribe what you have observed. 



3. In each segment, except those at the tip of the ab- 



domen, there are two breathing pores or spiracles, 

 one on each side. With the aid of a magnifier 

 look for these breathing pores near the lower 

 margin of the dorsal half of each segment. 

 When you have found the spiracles in four or 

 five segments, show them in your sketch (1, 

 above), and label breathing pores or spiracles. 



4. The spiracles lead into tiny elastic breathing tubes or 



trachece (singular trachea) which extend through- 

 out all parts of the body of the insect even into 

 the wings. The veins that you can see in the 

 wings contain these minute tubes. Describe 

 • the tracheae and state 

 their extent and their 

 connection with the 

 spiracles (Fig. 17). 



5. The tracheae have an elastic 



material in their walls, 

 so that when theyhave 

 been compressed, they 

 will spring back to 

 their former shape and 

 size as soon as the 

 pressure is removed. 

 Describe, now, the 

 structure of one of the 

 air tubes, and state 

 what action this struc- 

 ture makes possible. 



6. When the under or ventral 



half of the abdomen moves up into the dorsal 

 half — 

 a. Will the diameter of the abdomen be increased or 

 decreased ? 



Fig. 17. — Air tubes (tracheffi) 

 of an insect. 



