24 



by traps, poisons, and ferrets, under the supervision of the pro- 

 prietor. In this way 31,981 were killed, while it was estimated that 

 tenants at the thrashing had destroyed fully 5,000 more. Even then 

 the property was by no means free from rats.*^ 



During a plague of rats on the island of Jamaica in 1833, the num- 

 ber of rats killed on a single plantation in a year was 38,000. The 

 injury to sugar cane on the island caused by the animals was at that 

 time estimated at half a million dollars a year. * 



The report of the Indian Famine Commission presented to the 

 English Parhament in 1881 affords one of the best illustrations of 

 the number of rats that may infest a country. An extraordinary 

 number of the animals at that time inhabited the southern Deccan 

 and Mahratta districts of India. The autumn crop of 1878 and the 

 spring crop of 1879 were both below the average, and a large portion 

 of each was destroyed by rats. The resulting scarcity of food led to 

 the payment of rewards for the destruction of the pests, and over 

 12,000,000 were killed."^ 



MIGRATIONS AND INVASIONS. 



Migrations of rats have often been recorded. The brown rat is 

 known in Europe quite generally as the migratory rat. The Germans 

 call it the Wanderratte. Pallas narrates that in the autumn of 1727 

 this species arrived from the east at Astrakhan, southeastern Russia, 

 in such great numbers and so suddenly that nothing could be done 

 to oppose them. They crossed the Volga in immense troops. The , 

 cause of this general migration was attributed to an earthquake; 

 but since similar movements of the same species often occur without 

 earthquakes, it is probable that only the food supply of the animals 

 was involved in the migration which first brought the brown rat to 

 Europe. 



A seasonal movement of rats from houses and bams to the open 

 fields takes place in spring when green and succulent plant food is 

 ready for them. The return movement takes place in the autumn. 

 This seasonal migration is noticeable even in large cities. 



But more general movements of rats frequently occur. In 1903 a 

 multitude of migrating rats spread over several counties in western 

 Illinois. They were noticed especially in Rock Island and Mercer 

 counties. For several years previous no abnormal numbers of the 

 animals were seen, and their coming was remarkably sudden. An 

 eyewitness to the occurrence informed me that as he was returning 

 to his home one moonlit night he heard a general rustling in a 

 near-by field, and soon a great army of rats crossed the road in front 



n The Field (London), vol. 100, p. 545, 1902. 

 <> New England Farmer, vol. 12, p. 315, 1834. 

 c British MedicalJoumal, Sept. 16, 1905, p. 623. 



