Ecology of Animals 669 



soned thus: old maids keep cats, cats destroy field mice which in 

 turn destroy bumblebee nests. These latter are important for the pol- 

 lination of clover. The obvious conclusion is, the more old maids, the 

 more cats, the fewer field mice, the more bumblebees, and hence the 

 bumper crop of clover. True or not, this does show the interconnec- 

 tions that exist within a community. A glance at the diagram shows 

 how the complete removal of any one organism may upset the whole 

 complex. The truth of this has been shown repeatedly as man at- 

 tempts to modify his environment. 



rV^ggtation) 



Gray wolves , 



BiSon 



rsnakei 



Deer mice 



f Vegetation) 



Field Tnic e 



Badgers 



Toads 



Coyotes 



^ 



^ Spide 



Typhia 



(\'egetaUi 



egetatjon' 



r Marsh hawks 



Weevils Cnckets CraB' 



.^: 



Ground squirrels 



S9^*f *^ V 



Mole 



■ I 



h 



Pocket ' 

 Gophers 



Leal' 



"PA. 



"^A 



"Ofls v»< 



.M 



>^' 



.<^<^ 



Ants 



Sawfly lar\'ae 

 (^ Vegetation^ 

 Lepidopterous larvae 



Dry Vegetation 

 Seeds Roots 



Fig. 217. — Diagram show^ing the food relationships of a prairie community. 

 Arrows point from the animals eaten to those doing the eating. (From Animal Com- 

 munities in Temperate America by Shelford, The University of Chicago Press, copy- 

 right, 1913, by the University of Chicago.) 



At the basis of all these complex food relationships are the green 

 plants of the community which manufacture the food from carbon di- 

 oxide and water, thus making available energy for the growth of the 

 whole community. 



