UNITED STATES DEPARTMENT OF AGRICULTURE 
BUREAU OF BIOLOGICAL SURVEY 
WASHiNQTON, O. C. 
August 11;, 191 
Lir. Alex V/etmore 
San Juan, Porto Rico 
Dear Clr. Wetmore: 
I have your letter of July 30th enclosing a conruunication 
from Dr. Gruhts, Quarantine Officer for Porto Rico. You were 
quite right in making an immediate reply to the letter £ind giv- 
ing them all the information in your power. 
The suggestion that the mongoose should he examined for 
I 
plague fleas is an excellent one. They are, in rny judgment, 
much more likely to carry the insects than the house hat you 
mention. Nevertheless I think it very wise that a certain 
number of thei» should be examined, particularly as they resort 
to the same houses ?/herein are found 
rats. 
It is doubtful if in the tropics any more than in the Tem- 
perate Zone any rigid distinction can be made betwreen town rats 
and rats that live in cane fields and brush. Where snow fails 
there is a regular migration of rats in spring to fields from 
villages and even cities and back aguin to the shelter of houses 
in winter; and this is doubtless true, to some extent, even in 
the tropi’cs. The so-called roof rat, as you know, is the prin- 
cipal 'cane rat' and probably is responsible for more damage to 
cane than any other species; so that there are sound reasons, 
not only for examining; rats outside of town, but for inaugurating 
a war' of extermination a^inst.thern so far as it can possibly be 
done. 
