70 NATURE-STUDY LESSONS. 



20. (a) Observe the small openings which may be seen 



in large cabbage-larvae along each side of the 

 abdomen, in the same line as the yellowish 

 dots. These openings are the ends of tubes 

 that supply air. 



{b) If these breathing-holes become clogged what 

 will happen to the larva ? 



(c) Describe the way in which the larva breathes. 



21. How may gardeners prevent the destruction of 

 their cabbage-plants by these larvae? 



22. («) Observe the sloughs in the box where the larvae 



are confined. What are these ? 

 {b} Why does the larva cast its skin ? 

 When the larva casts off its outside covering it is said to molt. 



(c) Try to find how many times each larva molts. 



C. The Pupa, Sometimes Called the Chrysalis. 



23. Describe the change in the form of the larva. 



24. (a) Observe the larva in the breeding-box from 



day to day, and note the pupating among 

 the leaves. 

 (b) Describe the larva in its new form. 



The inactive form of an insect usually enclosed in a case and from which 

 the perfect insect emerges is called a chrysalis ox pupa, 



25. {a) How long is this chrysalis? 



{U) How is this chrysalis suspended ? 



{c) Where did the larva get the thread by which it 



attached itself to the twig ? 

 id) What is the color of the chrysalis ? 



26. Examine a case to discover whether it is thick or 

 thin. 



27. Draw the pupa-case. 



28. Open a pupa-case. 



