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mous percentage succumbs; the ratio of half males and half females 

 does not hold ; and ordinary conditions of life are hardly even favorable. 

 Nevertheless, the above proves emphatically that no rat eradication 

 can be effective unless the breeding is curtailed. Any campaign 

 against rodents must aim (a) to slaughter the greatest possible num- 

 ber of those already living and (6) to prevent the possibility of further 

 breeding. 



The existing rats are best attacked by trapping, by poisoning, and 

 by their natural enemies. Traps and poisons alone have been found 

 insufficient to keep pace with the rat's speed of multiplication. The 

 surest of the rat's enemies are his natural ones, and once they have 

 been loosed upon him his chance of escape is reduced. The cat, dog, 

 skunk, and other rodent foes, given a fair chance, quickly drive out 

 rats. But these animals do not eradicate the pest. The rats will 

 probably migrate to some other shelter, returning when their natural 

 enemies have quieted down. Absolute extermination is reached only 

 when conditions make the continuation of species impossible for the 

 rat. 



The size and frequency of rodent litters decreases proportionately 

 with every cutting off of food supples. Separate the rat from his 

 pabulum and he will not breed so freely nor so often as when he is 

 well fed. Destroy rat habitations and make it impossible for them 

 to find new nesting places, and breeding will virtually cease, since the 

 unsheltered progeny can no longer survive, and since the starving 

 parent rats are driven to cannibalism in the struggle for existence. 



Campaigns against rodents must cover five directions: (1) Trap- 

 ping, (2) poisoning, (3) exposing them to natural enemies, (4) cutting 

 off food supply, and (5) destroying existing nests at the same time 

 that the making of new ones is prevented. 



Parenthetically, it may be noted that while these principles apply 

 equally to the extermination of rats in cities and in country districts, 

 their application must vary according to the place. 



TRAPPING. 



The kind of traps to be used varies with the rodent to be captured 

 and the locality which it infests. 



CAGE TRAPS. 



The large 19-inch French cage trap gives good results where rats 

 are plentiful. It should be made of stiff, heavy wire and well reen- 

 forced, as a large, strong rat will force his head between the wires in 

 a weak trap and thus escape. Before setting, the lever on the trap 

 should be tested to see that it works properly. The trap should be 

 placed on a hard surface, with the rear end a little higher than the 

 entrance, so that the trap will close promptly. When setting the 



