DISTKIBUTION OF THE SPOTTED-FEVER TICK. 3 



65 miles from the United States boundary, directly north of the line 

 between Idaho and Washington. 



This tick does not seem to be limited particularly as regards life 

 zones. It appears to be most abundant in the Transition Zone, but 

 occurs commonly in the Canadian and Upper Sonoran Zones. It is 

 probably also to be found in the Hudsonian Zone. Specimens have 

 been collected at various elevations from slightly over 500 feet to 



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Fig. 1. — Map showing region in tlio L"nited States in whicbi the Rocky Mountain spotted- 

 fever ticli occurs. The degree of shading indicates tlie relative abundance of the tick 

 in different sections. (Original.) 



nearly 9,000 feet above sea level. The species seems to reach its 

 highest development and occur in greatest numbers between 3,000 

 and 5,000 feet. 



FACTORS INFLUENCING ABUNDANCE. 



The abundance of the Rocky Mountain spotted-fever tick is gi-eatly 

 influenced by the presence of numerous host animals, as well as such 



