16 MAN AND ANIMALS 



b) Communities of parks and pastures. — The ground and subterranean 

 animals of both pastures and lawns are (near Chicago) chiefly such 

 prairie animals as can live under the conditions of close grazing or close 

 mowing. This type of community is probably better developed in 

 the pastures than in the parks and lawns. The thirteen-lined squirrel, 

 the May beetle grub, and the earthworms are among the common 

 species. On the lawns a few grass-feeding species have a hazardous 

 existence. On the pasture land prairie animals are more abundant, 

 and an occasional prairie bird nests in a clump of weeds which the cattle 

 have not eaten. 



Shrubs, when present, are inhabited by the forest-margin species. 

 The trees present are inhabited by such forest animals as are able 

 to live without the characteristic ground conditions of a forest and 

 under the more severe atmospheric conditions. There are various 

 facts pointing to a difference in the animals attacking trees differently 

 located with respect to other trees; for example, trees standing alone 

 in open pastures probably have a very different fauna from trees of 

 the same species growing in the woods. This has not been fully investi- 

 gated, however. The trees of the parks and lawns are often somewhat 

 different from those of pastures, because of the introduction of many 

 trees not native to the region. The animal communities of trees fre- 

 quently include species introduced from Europe. 



c) Communities of lands devoted to cultivated annuals. — The communi- 

 ties of farm lands are made up of animals from the prairies, the forest 

 margin, and marsh vegetation, together with introduced species, such as 

 the cabbage butterfly, the wheat aphis, the Hessian fly, etc. 



d) Communities of orchards. — The communities of fruit-growing lands 

 are made up of the animals from the wild haw, wild crab, wild plum, and 

 other forest trees, the greater number of which are commonest on flood- 

 plains. There are also a number of introduced species. 



e) Communities of buildings. — The communities of barns, factories, 

 and dwellings include the common bedbug (introduced), the silver fish, 

 the cockroaches (introduced), various buffalo bugs of which several are 

 introduced; one (Dermestes lardarius Linn.) is dangerous to stored 

 materials and has been known to eat holes in lead pipe; while various 

 spiders, centipedes, and camel crickets occur. The house mouse, the 

 Norway rat, and the English sparrow have all been introduced. About 

 75 household species are to be expected in and about Chicago. 



/) Communities of polluted waters. — In connection with the building 

 of cities, we always find the introduction of sewage and industrial wastes 



