92 INSECTS. 



(5) That they end in a horny, hook -like tip. 

 4. Its prolegs. Make out : 



(a) That they are more membranous. 



(6) That they end in a circlet of minute hooks exactly 

 adapted for catching into a layer of silken threads, and 

 probably more serviceable to the caterpillar than are its 

 true legs. 



Compare this locomotor apparatus with that of an adult. 

 III. The Pupa. Study the chrysalis. Observe : 



1. The consolidation of head and thorax. 



2. The relative freedom of the abdomen and its capacity 

 for a slight twisting motion. 



3. The shape and surface markings of the chrysalis, and 

 the structure of the cremaster, in which the abdomen 

 terminates. 



4. The chitinous sheaths or cases of the appendages of 

 the body overlapping on the ventral surface. The cen- 

 tral ridge is that formed by the tongue case. Those next 

 on either side of it cover the first pair of legs. The next 

 cover the second pair of legs. The next are the antennae 

 cases. The next and largest are the wing cases. The 

 third pair of legs is concealed beneath the wing cases. 

 When the chrysalis is first formed, these parts are soft and 

 easily separable, but they become very solidly coherent 

 in an old chrysalis. 



5. The spiracles of the abdomen in their normal posi- 

 tion. The one on the first thoracic segment has been 

 crowded backward until it appears between the first and 

 second segments. 



From a comparison of larva and imago, it becomes evi- 

 dent that the quiescent pupal period is the period of 

 greatest developmental changes. It should be noted, how- 

 ever, that these changes have been begun in the larva; 

 that the insect begins its pupal period in possession of 

 the rudiments of its perfect organs. 



