EXERCISE 63 



Problem. What structures does an insect use in breathing? 



What to use. Some living insect in a bottle closed loosely with cotton or paper (a good-sized grass- 

 hopper or bumblebee will serve) ; some preserved specimens or some freshly killed large grasshoppers 

 or moths ; magnifying glass ; microscope. 



What to do. Watch the living insect with lens and note any movements of the posterior part of 

 the body, known as the abdomen. Note the tiny openings on the sides of the abdomen the spiracles. 



On a preserved or freshly killed insect examine a spiracle with a compound microscope. Using a 

 large grasshopper or moth, dissect out with sharpened needles, under water, the tubes leading from 

 these spiracles the tracheae. Study under the microscope. 



Record. Make an outline drawing of the side view of the insect, showing location of spiracles. 



Describe the movements of the abdomen of the live insect. 



Draw a sketch of the tracheae that you observed in the dissection, under the microscope. 



Questions. 1. What happens to air in tubes when the abdomen contracts ? when it expands ? 

 2. What structures in grasshoppers correspond to our nostrils ? to our bronchial tubes and lungs ? 

 to our chest walls ? to our diaphragm ? 



[68] 



