194 



Nature-Study Agriculture 



W. T. Skilling 



FIG. 148. A silky pupa case (Cecropia moth) and a 

 hard pupa case (Sphinx moth). 



do practically all of their eating and growing while in 

 the larval stage, and that is why the larger number of 

 insects are more destructive then than at any other time. 

 The pupa After a caterpillar has grown to its full size, it becomes 

 a pupa and remains at rest for some time perhaps 

 over winter protected often by a silky cocoon which 

 it has woven about itself (Fig. 148). The insect in the 

 resting stage is called a " pupa." Although motion- 

 less, or nearly so, its life is not at a standstill. A won- 

 derful change is taking place, so that when the covering 

 is broken open a full-grown butterfly or moth emerges, 

 ready to lay more eggs to start again this series of changes. 

 Thus, in such insects as the butterfly, where at each 



A change 

 during rest 



