34 THE ROCKY MOUNTAIN SPOTTED FEVER TICK. 
tion of the fever tick, the problem of control becomes very greatly 
simplified. The immature stages may be allowed to develop on the 
small mammals in the valley so long as the adult stage may be de- 
stroyed upon the domestic animals which are necessary for its 
development. 
Of course the reduction of the number of rodents in the valley, 
especially the Columbian ground squirrel, is advisable. These ani- 
mals are more or less serious agricultural pests. They destroy a 
considerable amount of produce, and the inhabitants of the valley 
are in the habit of waging warfare against them. Undoubtedly the 
damage done is abundantly sufficient to warrant this work. The 
reduction of the rodents should be encouraged both on general eco- 
nomic principles and because they carry the immature stages of the 
spotted-fever tick. This lne of work may well supplement the 
main work which must be dene with the larger domestic animals, 
and will undoubtedly hasten the removal of the fever tick from the 
valley. 
In one respect work against the rodents is of more than incidental 
value. It was found by Dr. Ricketts that five of these animals, 
namely, the gopher, rock squirrel, woodchuck, chipmunk, and moun- 
tain rat, are susceptible to spotted fever, and may serve as the 
original source of the disease in nature, or, at any rate, furnish a 
reservoir from which is derived the infection of human beings by 
the agency of ticks. The main point, however, is to destroy the tick 
which is necessary for the propagation of the disease, and this can 
be done by directing the principal efforts against the ticks on the 
larger animals which are under the control of man. 
There are several facts, in addition to the practical restriction of 
the adult fever tick to the larger domestic animals, which will serve 
to render a campaign of eradication feasible. One-of these is that 
the adult ticks are to be found on domestic animals or elsewhere dur- 
ing only a part of the year. Efforts toward eradication need not 
begin before March 1 and there would be no necessity for their con- 
tinuance far beyond June 15. This is the season when the work can 
be done most easily and with smallest risk to the stock. A line of 
attack extending throughout the year is entirely unnecessary. An- 
other favorable factor is the small number of live stock that would 
have to be treated. This is shown by the table below: 
TaBLE VII.—Numober cf live stock in Bitter Root Valicy. (U.S. Census, 1900.) 
Ravalli | Missoula 
County. | County. 
Bontoattle....... 0... .. eee eins eee oe ae ea AR 22,461} 13, 684 
15 10) 2c ee I EM ome me EC sony ie Pir AEE SiGe ee PG ie et RIE el ee ioe ox 6, 713 | 4,125 
Apt shah BRAS 2 ee Be aaere oe: eee. ee wR Wane Md i tloe DER eo ees a eh ae 18 | 36 
Pe ions ei tunn chien Pane GiB tte dee SUM Rain Ni Gatien EE cae ae ae een 58,212; 4,942 
