DISTRIBUTION. Lz 
Montana.—Beaver Head County, 3; Broadwater County, 2; Carbon County, 
1; Custer County, 1; Flathead County, 4; Gallatin County, 5; Granite County, 
5; Lewis and Clark County, 4; Lincoln County, 2; Madison County, 6; 
Meagher County, 3; Missoula County, 8; Park County, 2; Powell County, 3; 
Ravalli County, 7; Rosebud County, 4; Sanders County, 5; Silver Bow County, 
1; Teton County, 2; Yellowstone County, 1. 
Nevada.—Hureka County, 1; Humboldt County, 2; Lander County, 2; Lin- 
coln County, 2; Nye County, 3. 
New Mexico.—Rio Arriba County, 1; San Miguel County, 1. 
Oregon.—Baker County, 1; Crook County, 38; Grant County, 1; Harney 
County, 3; Klamath County, 1; Lake County, 1; Malheur County, 2; Sherman 
County, 1; Umatilla County, 2; Union County, 1. 
Utah.—Boxelder County, 2; Cache County, 2; Iron County, 1; Uinta County, 
1; Utah County, 8; Wasatch County, 3. 
Washington.—Asotin County, 2; Chelan County, 2; Douglas County, 1; Grant 
County, 1; Kittitas County, 1; Spokane County, 3; Stevens County, 14; Yakima 
County, 3. 
Wyoming.—Albany County, 3; Bighorn County, 6; Carbon County, 3; Fre 
mont County, 6; Latrona County, 8; Park County, 2; Uinta County, 2; Weston 
County, 1. 
The above is far from being a complete list of those counties in 
which the spotted-fever tick occurs, yet it gives a definite idea of the 
territory infested. It should be understood that the number of lo- 
calities given for a county does not represent the relative abundance 
of the tick in that county. The table includes only the number of 
localities from which the tick has actually been received. Greater 
population or a larger number of collectors in some counties has 
given more localities than in others, while the actual abundance of 
the tick may be exactly the reverse. Further investigation through- 
out the Rocky Mountain region will undoubtedly show the tick to be 
present in the majority of the counties included in the area shown to 
be infested in figure 1. Dr. E. E. Maxey? (1908, p. 4) reports that 
the tick has been found to occur in all of the counties of Idaho with 
the exception of Latah. 
As is pointed out in Circular No. 136 of the Bureau of Entomology, 
the fever tick is known to occur at various elevations from slightly 
over 500 feet to nearly 9,000 feet above sea level. The species occurs 
in greatest abundance in the area known as the transition zone. It is 
also commonly found in the Canadian and Upper Sonoran life zones. 
FACTORS INFLUENCING ABUNDANCE. 
The occurrence and abundance of this tick within a given locality 
are dependent, to a large extent, upon the presence of favorable con- 
ditions for development. These conditions are, first, the existence of 
the small mammals which serve as hosts for the immature stages; 
second, the presence of large mammals upon which the adults may 
1See Bibliography, p. 45. 
8464°—Bull. 105—11——3 
