PRESERVATION OF THE SPECIES 175 



Definitions. 



Postembryonic development, the changes taking place in 

 the development of an animal after birth or hatching. 



Larva, the active feeding stage. It is the first stage in 

 postembryonic development, and follows the gastrula stage. 



Pupa, usually a resting or quiescent stage. It is the 

 stage following the larva stage. 



Observations. 



1. Describe the appearance of the egg packet both as 

 seen with the unaided eye and with a hand lens. Find 

 the trapdoor. 



2. What is the difference between the appearance of the 

 larva and the pupa .■' How do their resting positions differ.'' 



3. What does the larva do when disturbed .■' Describe 

 any characteristic motions that you notice. 



4. Contrast the pupa with the larva under the same con- 

 ditions and note any differences. 



5. Where do you think the external openings of the 

 respiratory organs of the larva and those of the pupa are 

 located .' Give reasons for your answer. 



6. Into what does the pupa change ? Where must the 

 pupa be at this time .■' Is it easier for the pupa to stay at 

 the surface or at the bottom ? 



7. Examine an adult mosquito. State the kind of mouth 

 parts, the number and appearance of the wings, the ap- 

 pearance of the antennae. How does the male and female 

 differ in this respect .■' 



Suggested drawings. 



a. A diagrammatic drawing representing the jar of 

 water and showing the various positions assumed by the 

 wrigglers. 



b. Careful drawings of each stage. 



