8 ANIMAL BIOLOGY 



b. (Optional.) Shake some of the powder from a wing upon 

 a glass slide and examine it with a low power of the 

 compound microscope. The bodies that you see are 

 called scales. At one end of each scale you should 

 find a tiny stem by which the scale was attached to 

 the wing, and at the other end usually one or more 

 notches. Describe the shape of the scales that you 

 are studying, and make a sketch of one of them 

 much enlarged. 



6. (Optional home work.) Watch a butterfly in the field as it 



moves the wings in the act of flying. 



a. Will the downward stroke of the wings tend to lower or 



to raise the body? 



b. What effect will the upward stroke of the wings tend to 



have? 



c. In which of these two directions, therefore, must the 



butterfly strike the harder and more quickly in order 

 to raise the body in the air ? 



d. Since the weight of the body tends to bring the animal 



to the ground, in which direction must the insect 

 strike with the greater force in order to keep itself at 

 a given level in the air ? 



7. Some butterflies have a tiny pair of front legs that 



are usually folded against the thorax ; so that 

 you need to look very carefully before deciding 

 as to the number of legs present. 



a. How many pairs of legs has this insect? 



b. Are the legs long and slender or short and thick? 



c. Is each leg all one piece or is it jointed as in the 



human body? 



d. Examine the lower end of a leg and state how the 



foot is adapted for clinging to flowers. 



D. Make a drawing, natural size, of the upper or dorsal 

 surface of a butterfly. Label antennae, eyes, 

 proboscis, head, thorax, abdomen, wings, prin- 

 cipal veins of one wing. 



