240 THE HAUNTS OF LIFE 



It has its drawbacks, this instinctive capacity, 

 but it makes for success as long as the un- 

 expected does not happen. 



The fourth reason for the surpassing success 

 of insects in the system of animate nature is to 

 be found in their variability or plasticity, linked 

 with that of the plant world. While the 

 fundamentals of an insect's body are always 

 the same, the details vary without end, and 

 this has enabled insects to find an unusual 

 number of niches of opportunity -, especially in 

 their vital linkages with the likewise very 

 variable, flowering plants. Now, the more 

 niches of opportunity a class of animals can 

 find, the greater will be its success. 



A Russian naturalist, Chetverikov, has called 

 attention to a fifth reason for the success of 

 insects. It concerns their skeleton. In back- 

 boned animals the skeleton of living gristle 

 or bone is inside the body ; in insects and 

 other jointed-footed (Arthropod) animals the 

 skeleton of not-living chitin is outside the 

 body. Now it is argued that this entirely 

 different kind of body architecture made it 

 possible for insects to become very minute 

 without ceasing to be very effective. It was 

 more practicable to become small when the 



