60 BUTTERFLIES 



spiny creature blackish in color and marked by the curious 

 white saddle. A little later it moults again, retaining its 

 original coloring. At each moult, of course, it gets larger 

 and feeds moie freely upon the celery or other plant on 

 which it may happen to be. 



When the caterpillar becomes about half grown it takes 

 on a very different appearance from that of its early life. 

 The skin is smooth rather than spiny, and the general 

 colors are green, black, and yellow. The ground color of 

 the skin is green, which is marked with black cross- 

 bands along the middle of each body ring. On these 

 bands there are many large dots of orange yellow, the 

 whole coloring giving the insect a very striking appear- 

 ance, especially when it is placed by itself against a 

 plain background. When they finally become full grown 

 in this larva state, these caterpillars are almost two inches 

 long. 



The larvae of the Black Swallowtail have certain char- 

 acteristics in which they differ from many other cater- 

 pillars. After each moult they do not devour their cast 

 skins, which happens in the case of many of their relatives. 

 When feeding, as well as when resting, they remain ex- 

 posed upon the leaf and seem never to attempt to conceal 

 themselves, as is the habit with a large proportion of cater- 

 pillars. It is probable that this instinct for remaining ex- 

 posed to view bears some relation to the curious means of 

 protection possessed by this as well as other Swallowtail 

 caterpillars. When disturbed one of these larvae will push 

 out from just back of the head the strange-looking, orange- 

 yellow Y-shaped organ which gives off a very disagreeable 

 odor. These osmateria organs are generally believed to 

 be defensive against the attack of birds and various other 



