BUKEAU OF ENTOMOLOGY. 523 



formerly unsuspected localities. The area in which the disease car- 

 rier occurs was accurately mapped, as indicating the possible dis- 

 tribution of the disease. The investigation of this dangerous tick in 

 the Bitter Root Valley, where a very virulent strain of the disease 

 occurs, was continued along the lines mentioned in the last report. 

 Cooperation with the Montana Experiment Station and the Bureau 

 of Biological Survey was continued. Early in this investigation two 

 discoveries of great importance were made. One was that the tick 

 is remarkable m its ability to exist for a long period without feed- 

 ing. The adult tick was found to be able to exist for nearly two 

 years without a host. The other discovery is that the adult tick 

 is practically restricted to domestic animals, while the immature 

 stages live practically only upon certain small wild mammals which 

 never carry the adults. The first of these discoveries made it evident 

 that any plan of starvation, such as is practiced with the tick which 

 transmits Texas fever of cattle, is entirely out of the question. The 

 other discovery, however, at once indicated a feasible line of attack. 

 Since in the vast majority of cases the adult never develops upon 

 animals other than live stock, it is unnecessary to pay any attention 

 to the immature stages found commonly upon small wild mammals. 

 By destroying the full-fed females on domestic animals during the 

 spring and early summer, eradication may be accomplished. There 

 are several species of ticks wdiich occur in the Bitter Root Valley, 

 but the only one which need be considered is known as Der-macentor 

 veraistus. The others occur in so small numbers or are of such 

 peculiar habits that they can not serve as transmitters of the disease 

 in any important way. Since the one tick which shows practical 

 restriction of the adult stage to domestic animals is the only trans- 

 mitter of the disease which needs to be considered, the eradication 

 of the tick by dipping methods will undoubtedly eliminate the disease 

 from that region. 



A general suggestion toward this method of control was made 

 some years ago by the late Dr. H. T. Ricketts, but the work of the 

 bureau has placed the plan upon a certain basis and has made possi- 

 ble certain detailed methods of procedure which will be considered 

 fully in a bulletin shortly to be published. These plans relate espe- 

 cially to the Twitter Root Valley, where 15 or more deaths from spotted 

 fever occur annually, but the same basis for control may be emploj'ed 

 in Idaho and other States where the disease is found. 



During the investigation an effort was made to educate the people 

 in regard to the tick and the desirability of its control. The interest 

 of the public was sufficiently aroused to cause the erection of a 

 dipping vat at Florence, Mont., by popular subscription. 



Work upon the cattle tick was continued throughout the year. In 

 order to complete our knowledge of the effect of different climatic 

 conditions on the tick, experiments to determine the length of the 

 different developmental periods, and particularly the nonparasitic 

 jieriods, were continued. This information is of importance in the 

 work of eradication of this tick by the starvation or pasture rotation 

 plan. In this work the cooperative arrangements Avith the Tennessee 

 Experiment Station were continued. Experiments were conducted 

 which throw much light on the relation between rations and tick 

 attack. Additional experiments with feeding sulphur to cattle indi- 



