XX. GENERAL CONSIDERATIONS FROM THE STUDY OF 



INSECTS 



Problem XXXI. How iitscctfi bcrume jviiuicrs in life's race. 

 {Laboratory Man II al , Prob. .I'A'.l'/.) 

 (a.) Protective re>;cinblnnce. 

 (b) olg£'res.<:ivc resemblance, 

 ic) .Mimicry, 

 icl) Communallife. 

 (.e) Symbiosis, 

 (f) Parasitism. 



Insects are by far the most numerous of all animals. It is esti- 

 mated that there are more species of insects than of all other 

 species of animals upon the globe. Why should insects come 

 to have existed in so much greater numbers than other animals? 

 We cannot explain this, but some light is thrown on the problem 

 when we consider 

 some of the ways 

 in which insects 

 have become 

 winners in Ufe's 

 race. 

 y^^rotective Re- 

 semblance. — 

 When we re- 

 member that the 

 chief enemies of 

 insects are birds 

 and other ani- 

 mals which use 

 them as food, we 

 can see that the 



insect's power of rapid flight must have been of considerable 

 importance in escaping from enemies. But other means of pro- 



249 



The walking stick on a twig, showing protective 

 semblance. 



