SOCIAL AND COMMUNAL LIFE 4*3 



the males and females have given up the functions of food- 

 getting and of caring for their young ; did not the workers 

 do these things for them, the community would die out 

 quite as soon. 



The advantages of communal or social life, of co-opera- 

 tion and mutual aid are real. Those animals that have 

 adopted such a life are among the most successful of all 

 in the struggle for existence. The termite worker is 

 one of the most defenseless and for those animals that 

 prey on insects one of the most toothsome insects, and 

 yet the termite is one of the most abundant and success- 

 fully living insect kinds in all the tropics. Ants are 

 everywhere and are everywhere successful. The honey- 

 bee is a popular type of successful life. The artificial 

 protection afforded it by man may aid it in its struggle 

 for existence, but it gains this protection because of certain 

 features of its communal life, and in nature the honey-bee 

 takes care of itself well. Co-operation and mutual aid 

 are among the most important factors which help in the 

 struggle for existence. 



Commensalism. TECHNICAL NOTE. Examine ants' nests 

 to find myrmecophilous insects. If on the seashore search for hermit- 

 crabs with sea-anemones on shell. If inland, try to have some pre- 

 served specimens showing the crabs and sea-anemones. 



The phases of living together and mutual help just dis- 

 cussed concerned in each instance a single species of 

 animal. All the members of a pack of wolves or of a 

 honey-bee community belong to a single species. But 

 there are numerous instances known of the mutually 

 advantageous association of individuals of two different 

 species. Such an association is called commensalism or 

 symbiosis. 



The hermit-crabs live, as has been learned (p. 154), in 

 the shells of molluscs, most of the body of the crab being 

 concealed within the shell, only the head and the grasping 



