CHAPTER XIII 



INSECTS AND OTHER ORGANISMS 



The subjects considered in most of the chapters of this 

 book — feeding, shelter, reaction, and relation to surroundings, 

 family and social life, and especially the implications of the 

 struggle for existence discussed in the pages immediately 

 preceding — have combined to emphasise the importance of 

 other organisms, both plant and animal, in the life of insects 

 and also the importance of insects in their lives. A vast 

 number of insects feed, for example, on plants, with the 

 result that many herbs, shrubs, and even trees are destroyed 

 by them. Some plants have acquired the power of response 

 to the insect's presence and stimulation in the formation of a 

 special growth or gall, thus providing the insect with food 

 and shelter at the least possible disadvantage to the plant. 

 Such insects as bees and Lepidoptera which have developed 

 specialised modes of feeding on floral products, often benefit 

 the plants that they frequent by pollinating the blossoms 

 and ensuring the setting of seed. The plant- eating insects 

 are pursued and devoured by predaceous insects or invaded 

 and destroyed internally by parasitic members of their own 

 class, or eaten by relatively big creatures such as birds. 

 Many insects again live as parasites in or on the bodies of 

 larger animals, and themselves harbour minute parasitic 

 worms and protozoa. In this chapter it is proposed to 

 discuss only a relatively few examples of definite relations 

 between insects and other creatures that have an evident 

 bearing on the conditions of their hves. 



The interrelations between the various organisms 

 inhabiting any region become increasingly complex when 



380 



