The Struggle for Existence 117 



the more subtle and perfect linkage described by 

 Kemner. 



We cannot pass from the subject without recalling 

 the well-known linkage between the British "Large 

 Blue" butterfly and a common ant. The eggs of the 

 "Large Blue" are laid on the wild thyme, and the 

 small caterpillars feed for a while on the flowers. 

 When autumn approaches they go a-roving, and are 

 picked up by ants and taken into the recesses of the 

 nest for the winter. It is believed that the caterpillars 

 have an exudation that is very agreeable to the ants, 

 inducing them to wink at the unpleasant fact that the 

 caterpillars eat their grubs all the winter through. 

 When spring comes the well-fed caterpillars say fare- 

 well to their hosts, pupate in soft earth, and turn into 

 the beautiful blue butterflies. This is a good instance 

 of the subtle weaving of the web of life. What pat- 

 terns there are ! 



§13. (B) The Struggle for Existence. 



The second fundamental idea in Darwinism is that 

 of the Struggle for Existence, which the great master 

 realized with much more insight than some of his 

 disciples have shown. By the struggle for existence 

 Darwin meant not merely the jostling and elbowing 

 around the platter of subsistence — like pigs at their 

 trough ; he meant also the endeavors that birds make 

 to save their young ones in the cold spring or against 

 the glare of an unusually strong sun. He meant not 

 only the inveterate antagonism between the grass- 

 eating herds and the carnivores hungry for warm 



