58 BUTTERFLIES 



adorned with red or orange spots. These butterflies are 

 also characterized by certain pecuharities in the brandling 

 of the wing veins which will be found pictured in more 

 technical works. 



The caterpillars of these butterflies have the character- 

 istic form pictured on the plate of the Swallowtails op- 

 posite page 80. When full grown they are large, fairly 

 smooth-bodied worms, showing at most on the surface 

 sparse fine hairs or fleshy threadlike projections. Their 

 most characteristic feature is found in the scent organs 

 called osmateria situated in the back just behind the head. 

 These are thrust out, generally, when the caterpillar is 

 disturbed and appear as orange Y- or V-shaped organs 

 from which an offensive odor is commonly given off. 

 They are supposed to serve the purpose of preventing in- 

 jury by enemies, possibly birds, monkeys, and other 

 vertebrates. Structurally, they are like long tubular 

 pockets that can be turned inside out. When the pocket 

 is in place it is getting a pocketful of odors. When it is in- 

 verted it lets these odors free. On this account Professor 

 Comstock has aptly called these caterpillars "the polecats 

 of the insect world." 



When ready to pupate, these Papilio caterpillars spin a 

 web of silk upon some more or less flattened surface and a 

 loop of silk near by. They entangle their hind legs in the 

 former and keep their heads through the latter so the loop 

 supports the body a little behind the head. Then they 

 change to chrysalids which are held in place by these sets 

 of silken threads. 



The chrysalids are rather large and angular and gen- 

 erally take on colors approximating their surroundings. 

 They vary so much in different species that one familiar 



