28 ARTHROPODS 



These spines rub against the outer side of outer wings to 

 produce the sound. Is the noise made when the animal is 

 still or in motion? Give reason. Examine the outer wing 

 under the low power lens of microscope and determine if 

 possible which vein is specialized for noise making. Com- 

 pare the wing with that of female. Draw specialized wing 

 marking the specialization. 



Some Microscopic Views.^ — In order to understand bet- 

 ter the external structure of the grasshopper it will be 

 necessary to view some parts of it under the microscope. 



Cut off a portion of the large eye with a scalpel, turn it 

 over and scrape from it all the black portion leaving it trans- 

 parent or nearly so. Put this transparent membrane of the 

 eye on a glass slide with the outside up, moisten it with a 

 drop of water, and place on it a thin cover glass. Place this 

 slide on the stage of the microscope ' in the proper position 

 and observe it with a low power objective. What does this 

 show you about the large eyes? Each of these divisions 

 is called a facet. Observe the size and shape of the facet in 

 different parts of the eye. Are they all alike? 



Make a drawing of this view. 



Cut out a piece of the inner wing from near the center 



and mount it as the eye was mounted. Observe it with the 



low power objective. What do those veins now seem to be? 



Note the different kinds of veins and the structure of each. 



What do you think the veins are used for? 



Make a drawing of this view. 



With a scalpel remove from a segment of the abdomen 



a thin section of the outer skin containing a spiracle. Scrape 



Note.— For suggestions on how to use the microscope, see Ap- 

 pendix, I. 



