80 ARTHROPODS 



Note the general shape of the head, the large eyes, prom- 

 inent jaws and large lahmni. The most peculiar thing is the 

 enormous development of the lower lip, or labium. Open it 

 with the needle and note its structure. What use can the 

 animal have for such an organ. ? Do you think such a struc- 

 ture would help in gathering food? Why? Watch a live 

 specimen gathering food. This can be better noted 

 after putting in fresh dredging from the pond. 



Draw front view of head (X4)- 



(4) Note the legs. How and where are they attached? 

 Compare them with the legs of the adult. 



Observe the rudimentary wings. Are there two pairs? 

 To what are they attached ? 



(5) Count the segments of the abdomen. Do you find 

 spiracles along the sides? Since the nymph lives in water 

 it breathes air from the water instead of from the atmos- 

 phere as in the adult. The water is taken in at the anal 

 opening, carried over trachael gills, and after purifying 

 the blood, is expelled again at the same opening. Study 

 this method of respiration. Find and draw gills. 



Draw nymph (X2). 



(6) Get a number of specimens of different sizes illus- 

 trating different stages of growth and make a series of 

 drawings showing the development of the dragon fly. 



Habits. — Watch the dragon fly in motion. Why has it 

 such a jerky, uncertain motion? Does it seem to have the 

 power of going in a definite direction? What is its food? 

 How does it obtain it? Why is it called mosquito hawk? 

 Why does it spend so much time near water? How does 

 the dragon fly spend the winter? At what time in the 

 spring does it appear? Is the development complete or in- 



