REPORT OF THE SECRETARY. 121 



new conditions met with in its continued spread to the north and to 

 the east. The work upon tobacco insects has progressed, and that 

 upon sugar cane and rice insects has made a good start. The work 

 upon the pear thrips in Cahfornia, practically completed from the 

 investigational side during the previous fiscal year, has been carried 

 on by the conduct of large demonstrations wliich have indicated in a 

 very perfect way the practical value of the conclusions previously 

 reached. Studies and demonstrations with the codling moth have 

 been continued. The work upon the grape root-worm has been com- 

 pleted, and an interesting investigation has been followed in the 

 study of arsenic accumulations in the soils in sprayed woodlands, 

 orchards, and vineyards. Demonstration spraying has been carried 

 on against the plum curcuho, and the investigation of cranberry 

 insects is nearly completed. Further studies on the green bug, the 

 joint-worms, and the Hessian fly have been carried on, and studies 

 of two new pests, namely, the Xew Mexico range caterpillar and the 

 alfalfa weevil in the "West, have been begun. The work against truck- 

 crop insects in Tidewater Virginia, in North Carolina, Colorado, Mis- 

 sissippi, California, and southern Texas have resulted in results of 

 value to the growers of those regions. Studies of the house fly have 

 been continued. The work on the Texas cattle tick has been for- 

 warded, and a thorough investigation of the tick which carries the 

 spotted fever of human beings in the Rocky Mountain regions has 

 been begun. The investigations of stored-product insects have com- 

 prised a careful consideration of the point of infestation of export 

 flour and experimental work in rice mills of the South. The work in 

 bee culture has been devoted largely to the study of bee diseases, 

 but other investigations in this direction are under way. 



BUREAU OF BIOLOGICAL SURVEY. 



The Bureau of Biological Survey has continued its investigations 

 of the economic relations of our wild birds and mammals with special 

 effort to render its work of practical importance to the farmer and 

 stock grower. It is gratifying to note that as the work of the Bureau 

 becomes more widely known it meets with increasing approval and 

 support from those it is intended to benefit. A remarkable and, until 

 recently, quite unexpected broadening of the work of the Survey into 

 the field of the preservation of the public health has resulted through 

 the fact that some of our native wild mammals have been proved to 

 be disseminators of such fatal diseases as the bubonic plague and the 

 spotted fever. 



RATS AND THE BUBONIC PLAGUE. 



So important is the rat in its relation to the public health that its 

 extermination has become one of the serious problems of motlern 

 times, both in the United States and m foreign countries. Since it 



