THE STRUGGLE FOR LIFE 



219 



by parasitic insects. This is only one of the many re- 

 corded instances. 



Social Organization. We have already observed that 

 insects qualified to conduct their affairs in colonies and 

 societies are eminently successful. This congregating 

 together is not confined to adults. Certain caterpillars 

 possessing the property of emitting nauseous odors are 

 iiTcuarious. The meaning of this habit seems evident: 



o O 



when many individuals emit this offensive odor at the 

 same time, they become enveloped in an atmosphere 

 which effectively serves to repel attack. 



Feigning Death. Motionless objects attract notice less 

 readily than moving objects. Upon the slightest dis- 

 turbance snme insects and many caterpillars become 

 inactive, and for a time remain motionless. In the case 

 of the attack of another insect with motives of conquest 

 rather than an appetite to satisfy, this inactivity may 

 allay further antagonism. 



How can we account for the evolution or development 

 of these various traits? We have observed that no two 

 individuals arc identical, and that variation in struc- 

 ture and habits exists. Under "Artificial Selection" 

 our attention is called to the fact that under the intelli- 

 gent selection of man these variations can be perpet- 

 uated and become more marked. It remains for us to 

 see if some such selection of forms can be found in 

 nature, a selection which by unions strengthens pro- 

 pitious variations or traits. 



Artificial Selection. - The character of our domestic 

 animals is largely due to the intelligent selection exer- 

 cised by man. We have the sagacious shepherd dog, 

 the bloodhound with wonderful keenness of scent, the 



