70 Laboratory Guide in Zoology 



XIV. — Note the structure and size of the dragon-fly's wings 

 as compared with those of' other insects. Notice the 

 relative size of the front and hind wings. What bear- 

 ing do these characters have upon the habits of Hfe of 

 the dragon-fly ? 



XV. — Study the veins of the wings. Near the middle of 

 the front margin find a slight notch connected with a 

 short transverse vein. This structure is called the 

 nodus. Its presence is an important characteristic of 

 this group of insects. 



XVI. — Notice the legs. Are they large or small ? Does 

 the dragon-fly walk much ? 



XVII. — Beginning with the segment next the body find 

 the following parts of one of the legs : coxa, trochanter, 

 femur, tibia, and tarsus. 



XVIII. — Study the claws on the tarsus. To what special 

 use are they likely to be put .' 



XIX. — Find the ten segments which "compose the abdo- 

 men. The division between the segments is indicated 

 by ridges which completely surround the joints. Bear 

 this in mind when determining the segments nearest the 

 thorax. 



XX. — In any single segment point out the parts, called 

 the tergite, pleurite, and sternite. (Refer if necessary 

 to page 68.) 



XXI. — ■ Find the spiracles, or breathing pores, on the pleu- 

 rites. What is their position ? 



XXII. — Study the terminal segment. In the female this 

 segment is large and rounded ; in the male it has four 

 pointed appendages. 



XXIII. — Make a drawing of a dragon-fly as seen from 

 above. 



