260 BUTTERFLIES 



flies lay their eggs upon tlie flower buds of various plants, 

 especially those which have clustered racemes of blossoms. 

 These eggs hatch into minute slug-like larvae which feed 

 upon the buds, commonly burrowing through the calyx 

 lobes and devouring the undeveloped stamens and pistils 

 inside. They finally change to chrysalids, which are more 

 or less securely attached to a central flower stalk, from 

 which in due time the butterflies emerge. So far there is 

 nothing remarkable about this story of the life of the 

 Spring Azure, but that is yet to come. 



These little caterpillars are subject to attack by tiny 

 parasitic flies which lay eggs in their bodies. Each egg 

 hatches into a still more tiny maggot that lives at the ex- 

 pense of the tissues of the caterpillar and finally kills it. 

 When one of these little caterpillars has its head buried in 

 the round ball of a flower bud, about half of its body is ex- 

 posed defenseless, so that the little fly that lights upon it to 

 lay her egg cannot even be dislodged by the head of the 

 caterpillar, as is often the case with other species. There is 

 a very curious provision for defense, however. If you look 

 carefully through a lens at the hind part of the body you 

 will find a little opening on the back of the seventh abdom- 

 inal ring. This opening leads to a sort of tiny pocket, a 

 pocket which the caterpillar can turn inside out when it so 

 desires. Now the curious thing about it is that the cater- 

 pillar, while this pocket is concealed in its body, is able to 

 secrete in it a drop of liquid which we presume to be sweet 

 to the taste. When the little pocket is partly filled with 

 this drop of liquid the caterpillar turns it inside out in such 

 a way that the liquid drop remains in position on top of the 

 protruded pocket. 



Perhaps you ask what is the good of all this complicated 



