32 2 FIRST LESSONS IN ZOOLOGY 



ocean and part in streams. Many animals are trans- 

 ported long distances involuntarily. Rats and mice in- 

 vading a ship from wharves at Liverpool sometimes get 

 carried across the Atlantic Ocean to America. In fact 

 the common black rats and brown rats of the houses and 

 barns over this whole countr)- are not native rats at all, 

 but are descendants of European rats unintentionally 

 brought across the ocean in ships. The same is true of 

 man}' of the insect pests which trouble us ; for example, 

 the Hessian fl}', which does great damage to wheat, the 

 cockroaches of our houses and the carpet beetles or buffalo 

 bugs which attack rugs and carpets. Sometimes a boring 

 insect lying snugly in a log gets carried down a river, 

 out into the ocean, and by means of ocean currents far 

 away to some island where it may crawl out and lay eggs 

 and so establish itself in a new countr)'. Sometimes 

 animals are intentionally imported by man from foreign 

 countries. The introduction of the English sparrow into 

 this country and the rabbits into Australia are examples 

 of unfortunate experiments along this line. 



Map showing the distribution of animals. — Zoologists 

 have been studying the distribution of animals so long 

 that they have been able to map out the range of many 

 of the well-known kinds. On a map of the ^\'orld the}- 

 indicate, b}^ shading, all those regions in which lions 

 exist; all those in which elephants live, and all those in 

 which humming-birds are found. Now this kind of map- 

 making reveals man)' things of interest antl throws much 

 light on the relations of animals to climate, to geography, 

 and to each other. 



Such zoological map-making ma)' be restricted to a 

 limited localit)', and is the best wa)- for beginning stu- 

 dents to study distribution. On a large sheet of strong 

 paper a map of the region about the schoolhouse, sa)- one 

 or two miles square, should be made, with all the streams, 



