r-iUTlTAL AID AND COMMUXAL LIFE AMONG ANLMAI.S 3,^.'^ 



./r communities wliich spread o . er many acres. Tliey tell 

 t^ach other by shrill cries of the ai)i)roach of enemies, and they 

 seem to visit eacli other and to enjoy each other's society a 

 great deal, althoiioh that they afford each other nnich actual 

 active help is not apparent. Pjirds in migration are grega- 

 rious, although at other times they may live comparatively 

 alone. In their long flights they i^eep together, often with 

 definite leaders who seem to discover and decide on tlie course 



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1-iG. 23.j.^rrairic duKs. (A<la|)te«l from pJiolu- 

 graph \)y Merriaiii.) 



/ of flight for the whole great flock. 

 ■i > ' The wedge-shaped flocks of wild 



f J- geese flying high and uttering their 



sharp, metallic call in their south- 

 ward migrations are well known in many parts of the Unitetl 

 States. Indeed, the more one studies the habits of animals 

 the more examples of social life and mutual help will be found. 

 Probably most animals are in some degree gregarious in habit, 

 a.nd in all cases of j>Tegariousness there is probabl}- some de- 

 gree of mutual aid. 



An interesting series of gradations from a strictly solitary 

 through a gregarious to :t.r. eial)orately specialized comnumal 

 life is show'n by the bees. Although the buml>lel)ee and tlie 

 honeybee are so much move- familiar to us than other bee kinds 

 that the communal life exemi^lified bv them mav have come 



I ^ k 



to seem the usual kind of l)ee life, yet, as a matter of fact, tlierc 

 are many more solitary bees than soci;d ones. The general 

 character of the domestic economy of the solitary bees is well 

 shown l)y the interesting little green carj)enter bee. C'rrafitui 

 dupla. Each female of this species bores out the i)itli fronv 

 five or six inches of an eldcM* branch or raspl)erry cane, and 



