IIG ANNTAl. KKTOHTS OF DKr.VHTM KNT OF AUKICULTURE. 



witli which we have constant trade relations emphasizes the danger 

 of tlie hiniling of phigue-stricken rats from incoming ships, and 

 renders imperative tlie need of perfecting means for the destruction 

 of these vermin, nt)w believed to be the chief means for disseminating 

 this dread disease. During the past year experiments were continued 

 lo discover olTective means of reducing the numbers of this pest, 

 without the discovery, however, of methods superior to those recom- 

 meniled in Farmers' Bulletin 309. While poison and traps must 

 continue to be the chief means of reducing the numbers of these 

 mischievous rodents in public buildings, dwellings, stores, and ware- 

 houses, it can not be too strongly urged that preventive methods are 

 vastly easier, much more effective, and in the long run cheaper. The 

 rat-proofing of buildings, especially those in which foodstuffs are 

 stored, should be insisted on as far as possible. This precaution, 

 coupled with the withholding of food so as to reduce reproductory 

 powers and make trapping and poisoning effective, will result in ma- 

 terially reducing the number of the pests and lessening the danger 

 from them. 



GROUND SQUIRr'eLS AND THE PLAGUE. 



Throughout much of the region west of the Mississippi River ground 

 squirrels of many species abound. In past years much time and atten- 

 tion has been given to the study of the habits of these rodents and 

 of methods of controlling them, since wherever found they are ex- 

 ceedingly destructive to farm crops, and in irrigation districts they 

 do much damage by burrowing into embankments, thereby causing 

 costl}' breaks. The spread of bubonic plague by rats to the ground 

 squirrels of California, discovered by the Public Health and Marine- 

 Hospital Service, is a matter of national importance, since there is 

 danger not only that the disease may become endemic in that par- 

 ticular State but eventually, through the agency of other species of 

 ground squirrels, spread to neighboring States and thus threaten the 

 whole country. As yet plague germs have been found in only one 

 other native rodent, the California wood rat, and in only one indi- 

 vidual of that species. The destruction of a mammal so numerous 

 nnd so widely distributed as the California ground squirrel is a 

 very serious undertaking on account of the great cost involved, and 

 yet safety from the plague can apparently be fully assured in no 

 other way. 



During the year careful experiments were made to discover, if 

 possible, better and cheaper methods of poisoning ground squirrels, 

 and a circular embodying the results of these experiments was pub- 

 lished. The formulas in Biological Survey Circular TG can be con- 

 fidently lecommended for cheapness and effectiveness. This cir- 

 cular has been widely distributed throughout California, with a view 



