INTRODUCTION 7 



active in freeing itself from the exuviae. But as soon as it 

 is free it is likely to rest quietly for some hours while the 

 tissues of the new skin are hardening. Then it begins 

 feeding upon the leaf again and continues taking its meals 

 at more or less regular intervals for several days. By that 

 time it will again have reached its limit of growth within 

 this second skin and the process of moulting must be re- 

 peated. It takes place in the same way as before and the 

 caterpillar enters upon the third instar of its larval life. 



This process of feeding and moulting is continued for 

 several weeks, the number of moults being usually four. 

 During the later stages the increase in size is more marked 

 each time the skin is shed, until the caterpillar finally 

 reaches its full growth as a larva and is ready for the won- 

 derful change to the quiet chrysalis in which all its cater- 

 pillar organs are to be transformed into the very different 

 organs of the butterfly. , 



In the case of butterfly larvae one of the most interesting 

 features of the growth of the caterpillar is that of the re- 

 markable changes in colors and patterns of marking which 

 the caterpillar undergoes. One who had not followed 

 these changes would often be at a loss to recognize cater- 

 pillars of slightly differing sizes as belonging to the same 

 species. These changes commonly show a remarkable 

 adaptation to the conditions of life, and generally tend to 

 the concealment of the caterpillar upon its food plant. 

 The stages of growth of the green-clouded swallowtail cater- 

 pillar are illustrated on plate opposite page 80. 



Before each moult the caterpillar is likely to spin a 

 silken web upon the leaf surface. It then entangles its 

 claws in the web to hold itself in place while the skin is 

 cast. (See plate, page 17.) 



