April, ’18] PARKER: ROCKY MOUNTAIN SPOTTED FEVER TICK 
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SOME RESULTS OF TWO YEARS’ INVESTIGATIONS OF 
THE ROCKY MOUNTAIN SPOTTED FEVER TICK IN 
EASTERN MONTANA 1 
By R. R. Parker, Bozeman, Mont . 
Until 1915 the occurrence of Rocky Mountain spotted fever in east¬ 
ern Montana was thought to be limited to Carbon County. Though 
this is now known to be untrue, still the spring of 1915 was the first in 
which the disease was sufficiently prevalent to attract marked atten¬ 
tion. The infected territory included most of the eastern counties, 
particularly the central and southern. So many cases appeared and 
in such a large area that a brief survey of conditions was undertaken. 
The need for extensive research was immediately apparent. Inten¬ 
sive studies were carried on at Powderville in southern Custer County 
in 1916 and at Musselshell in Musselshell County in 1917, infection 
having existed at both localities. Trips to other localities and cor¬ 
respondence have increased the comprehensiveness of the work. 
The character of the country was found to have a fundamental 
influence on the abundance of ticks and a brief statement of condi¬ 
tions is necessary before proceeding. Though there is some variation, 
the greater part of the country conforms to two types,—the prairie 
type and the hill type. In the former the country is very bare, sage 
brush and prairie grasses the predominant plant life, while tree growth 
is mainly confined to the river banks. The Powderville studies were 
carried on in this sort of country. The work at Musselshell, however, 
was in the hill type. There the formation consisted of hilly, pine- 
wooded areas separated by narrow valleys, from which much narrower, 
many branched coulees extended far back into the hills. The valleys 
and hills were joined by very steep, rocky slopes, that were frequently 
wooded. 
Abundance of Ticks. —One of the first observations of importance 
was that in most regions ticks are really numerous only during occa¬ 
sional seasons. The year of 1915 was one of great abundance in many 
places. Occasional areas are found included in the prairie type, how¬ 
ever, where ticks are either abundant each year or at least at more 
frequent intervals than on the prairie itself. Such areas are usually 
small and the difference in the abundance of ticks is due to changes in 
the fauna dependent on highly localized changes in the vegetation. 
A good example is furnished by the U-shaped bends of the Powder 
river where the enclosed land frequently is heavily wooded and there 
1 Contribution from the Montana State Board of Entomology. 
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