190 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 11 
is abundant underbrush. Such places are exceedingly favorable for 
the increase of certain species of tick hosts, which, under prairie con¬ 
ditions, are never numerous enough to be of importance. 
Wild Mammals as Tick Hosts. —The conclusions regarding the 
importance of various wild mammals as tick hosts are based on the 
examination of 1,703 animals belonging to about 30 species. Under 
prairie conditions 11 species were found to be hosts of larval and nym- 
phal ticks. These were jack rabbits, cottontail rabbits, deer mice,, 
field mice, chipmunks, pack rats, kangaroo rats, striped spermophiles, 
grasshopper mice, prairie dogs and porcupines. Porcupines, grass¬ 
hopper mice and probably prairie dogs are of little importance. On 
the other hand, in the hill country at Musselshell, where the country 
was rocky and more or less wooded, deer mice and chipmunks were 
the only generally distributed hosts of the immature ticks that were 
of any importance. Rabbits and pack rats, normally rather numer¬ 
ous, were very scarce in 1917, but would be factors to be reckoned 
with whenever abundant. Field mice were important wherever con¬ 
ditions favored their presence in large numbers. 
As hosts of the adult ticks wild mammals were found to furnish 
three,—jack rabbits, porcupines and coyotes. The importance of 
coyotes is uncertain. 
Of the animals above mentioned, jack rabbits, porcupines, deer 
mice and field mice are deserving of further discussion. 
Jack Rabbits .—The jack rabbit merits distinction as the most impor¬ 
tant wild mammal of eastern Montana in relation to the spotted fever 
tick. This is due to the following reasons: first, it is the only animal 
known to harbor all three stages of the tick; second, according to all 
indications it can maintain an infestation of ticks without the pres¬ 
ence of domestic animals; third, it is generally distributed in all parts 
of eastern Montana; fourth, it has a wide travelling radius; fifth, it is 
susceptible to Rocky Mountain spotted fever 1 ; sixth, there is reason 
to believe that this rabbit may play an important part in the spread 
of the disease both extensively and intensively. 
Under prairie conditions, when ticks were not at all abundant, 65 
of 84 jack rabbits examined were tick infested (77.38 per cent). Fifty- 
six (66.66 per cent) were infested with adults. This was an average 
of 1.87 adults per rabbit, whereas the average for horses examined 
during the same period was 1.44. The greater percentage of females 
on horse, however, would probably more than discount the numerical 
superiority in favor of the rabbit, and in years of real tick abundance 
1 This has been demonstrated by work recently carried on at the Harvard Medical 
School under the direction of Dr. S. B. Wolbach, who has lately contributed greatly 
to the knowledge of the etiology and the pathology of the disease. 
