CHAPTER XIII 



INSECT ECOLOGY 



Ecology is the physiology of organisms in relation to environment. 

 It is the physiology of entire organisms rather than of organs. It deals 

 with the reactions of organisms to the conditions of their existence, 

 including the modification of these reactions in relation to changes of 

 environment. 



Though its subject matter is primarily animals and plants, ecology 

 is based upon all the sciences, and cannot be pursued most precisely 

 without the aid of some mathematics. 



Insect life in its omnipresence and diversity affords countless illus- 

 trations of ecological principles, under which innumerable isolated 

 observations fall into organization. 



The qualitative study of the subject is simply a matter of accurate 

 and thorough observation and correct inference, with the aid of the 

 simplest kind of experimentation. Even in quantitative investigation, 

 the ecological principles may be brought out with the use of such 

 inexpensive means as thermometers, ice-boxes, weather maps, etc. 

 For the most refined work, however, elaborate appliances for controlling 

 ecological factors are often necessary. 



It should be remembered that the study of insects alone gives only 

 a partial understanding of ecology, with an imperfect perspective of 

 the subject. 



The ecology of individuals is known as Autecology; that of com- 

 munities, as Synecology. 



I. CONDITIONS or TERRESTRIAL EXISTENCE 

 i. SOIL 



The edaphic conditions of existence (those relating to the soil) are 

 the same for animals and plants, but are utilized in different ways by 

 these organisms. Plants can utilize inorganic constituents of the soil 

 as food, but animals can not. All the food of animals, with such 

 exceptions as water and salt, is derived in the last analysis from plants. 



Structure. The retention of water by the soil depends largely upon 

 the size of the soil particles; soil of small particles holding more water 



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