30 ZOOLOGY DIRECTIONS 



5. Note the adaptation of the labium (lower lip) for grasp- 

 ing food. Examine preserved specimen and with forceps draw 

 the labium forward to fully extended position. Draw side view 

 and dorsal view of labium, fully extended, X5. 



6. Draw the entire animal, dorsal view X4. Label the 

 head, the thorax (the part bearing the legs), and the abdomen. 



7. Into what kind of an animal does the nymph transform? 

 See demonstration. Notes required. 



8. Define metamorphosis. Notes required. 



9. The three plate-like gills of the damselfly nymphs con- 

 tain the air tubes (tracheae), while in the dragonfly nymphs 

 the posterior part of the intestine is modified and contains 

 tracheal filaments. Air and not blood fills these tubes, and 

 aerates the tissues. 



II. Damselfly Nymph 



1. Describe the habits of the live animal, its methods of 

 locomotion, habit of resting, etc., while in an aquarium. De- 

 scribe fully. Notes required. 



2. Does the animal feign death? If so, under what condi- 

 tions and for how long? Notes required. 



3. Draw the entire animal X4, dorsal view. 



4. Draw X5, a plate-like gill. 



5. Examine the expanded labium from the side and from 

 the ventral surface. Compare with labium of dragonfly. 



6. Into what kind of an animal does the nymph transform? 

 See demonstration. 



REFERENCE 



Wilson, C, B., 1920. Dragonflies and Damselflies in relation to 

 pondfish culture, with a list of those found near Fairport, 

 Iowa. Bull. U. S. Bur. Fish., 36 (Doc. 882) : 182-264. 



