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indoor rats living in the houses and those living in the coffee-plantations 

 and further the considerable number of fleas infesting the latter, the 

 possibility of rat plague being transmitted from one village to another 

 by these indoor-rats, living out-of-doors, cannot be held to be 

 •exceptional. 



The second section covers investigations concerning the biology of 

 Javanese house and field-rats. There are two varieties of house-rat 

 in Java, namely the larger, Mus rattus griseiventer, Bonh., and the 

 smaller, Mus rattus concolor, Blyth. Though morphologically distinct, 

 these two varieties do not differ in their habits ; being climbing species, 

 they both live by preference in the upper parts of houses and are there- 

 fore of great importance as regards human plague. In view of the 

 fact that Java is very thickly populated, the villages being at compara- 

 tively short distances from each otheY, about three-quarters of a mile 

 on an average, it was of interest to ascertain whether house-rats were 

 really incapable of moving from one village to another. In certain 

 experiments it was found that from 5 to 9' 6 per cent, of the rats caught 

 in the rice-fields, at an average distance of about 650 yards from the 

 nearest village boundary, were house-rats ; the rest were all field rats. 

 From the X. cheo'pis index on the former, they must be held to have 

 emigrated from the houses and to be living in the fields temporarily. 

 In July 1913 an outbreak of rats was reported in some coffee planta- 

 tions in the district of Malang, Cqffea robusta being chiefly affected. 

 According to Dr. Wurth, the fact that Cofjea liberica (Liberian coffee) 

 and Coffea arabica (Java coffee) have not such a strongly developed 

 pith or so soft a bark, accounts for their comparative immunity. 

 The author commenced an investigation as to the rats on the Kali 

 Tello and Alas Tledek plantations and found that there were from 36' 7 

 to 45 per cent, house- and from 63' 3 to 55 per cent, field-rats. Investi- 

 gations made in Java- and Robusta-coffee plantations (where there 

 had been no outbreak) showed 84*5 to 92*2 per cent, of house-rats. 

 They were therefore not responsible for the outbreak, and form the 

 chief portion of the normal rat population of the coffee-plantations. 

 The smaller examples, M. concolor, were mainly represented and it 

 is supposed that these were driven out of the houses by the larger 

 M. griseiventer. Their food-stores always consisted of the young 

 shoots of Saccharum s-pontaneum, L. (wild sugar-cane) and the fruit of 

 Phyllanthus emblica, L., which grows wild in the plantations. They 

 do not therefore damage the coffee-trees. 



"O" 



In Java the field-rat is represented by M. rattus diardii, Jentink. 

 It is normally present in the proportion of from 1"6 to 15' 1 per cent, 

 in coffee-plantations, but this rises to 55-63"3 per cent, in coffee- 

 plantations where the crop has suffered considerable damage from 

 a sudden influx of rats. It may therefore be assumed that the injury 

 to coffee is caused by rats which migrate and that these are field-rats. 

 No definite reason can be assigned for their attacking coffee which is 

 untouched by the normal rat population, but it may be supposed that 

 the latter find the food they prefer more easily than those migrants 

 suddenly placed in strange surroundings. 



