THE CYCLE OF LIFE 



17 



by the fi nger. Photographed 

 from life> 



stems and leaves. This caterpillar no longer requires 

 a milk diet. 



Its horns, present from birth, 

 are now even more noticeable 

 and their use is more readily 

 discerned. For, when disturbed 

 by any object other than one 

 of its mates, the caterpillar pro- 

 jects its soft, fleshy, orango- 

 yellow horns from behind the 

 head. The position of the 

 horns, their formidable appear- 



FIG. 18. Caterpillar of black 



ance, and the act Of protrild- swallowtail protruding horns 



(osmateria) upon being touched 



ing them, all tend to frighten 



away approaching foes. There 



still remains, as a last and most effective means 



of defense, a repulsive odor arising from these horns, 



sensible ten or twelve feet away. This offensive odor 



saves many a caterpillar from the destructive beaks of 



insectivorous birds. 



Sociability is not one of the characteristics of this 

 immature butterfly. If one caterpillar encroaches upon 

 the other's territory, violent displeasure is manifested 

 by the dashing of the head from side to side. Never at 

 such times are the horns protruded, nor is the offensive 

 odor emitted. Why? 



At about three weeks of age the larva has grown until 

 it is about as many inches in length, has changed its 

 skin five or six times, has discarded the tubercles and 

 spines so prominent in the young thing just out of the 



egg. It is ready to become a chrysalis, a pupa, an in- 



2 



