4 LEAFLET 109, U. S. DEPARTMENT OF AGRICULTURE 
their roost with a chemical substance to which they object. Occasion- 
ally in large old buildings not only will shutting out the bats be found © 
impracticable, but the location of the roost will prevent the successful 
use of arepellent. In such cases fumigation with a poison gas may be 
necessary, with destruction of the bats themselves. 
THE MOST SATISFACTORY and the only permanent way of obtaining 
freedom from the bat-roost nuisance, however, is to shut the bats out. 
This may be called “bat proofing” the building. 
Bat Proofing Frequently there are only a few small entrances to 
Buildings the bat roost, and in such cases bat proofing is rela- 
tively simple. It is necessary only to close the open- 
ings with strips of metal or wood or seal them by plugging the smaller 
cracks with rags or other soft material. 
In cases where clapboard siding provides numerous openings, as 
under the overhang (fig. 1), or in very old large frame houses where 
warping, shrinking, and decay have left many suitable entrances, a 
simple and inexpensive means of shutting out the bats is found in the 
use of oakum. This is a tarred-hemp fiber used for calking ships, 
and it packs easily and firmly into any small crack. The tar binds 
the fiber so that it is not easily dislodged and, serving as a repellent 
to the bats, it also lessens the probability of their attempting to 
squeeze through it. A tire tool is convenient for packing the oakum 
into the openings. Equipped with a good ladder and a few pounds 
of oakum, one can in a few hours’ time effectively seal against bats 
all the small openings in almost any house. 3 
In closing the entrances used by bats it is necessary that 1 or 2 be 
left open until after nightfall, so as to allow egress of the bats, and 
thus shut them out and not in. Ordinarily during midsummer all 
the bats will have left the roost within 15 minutes from the time the 
first one starts, but after their accustomed routine has been thus upset, 
several hours may elapse before the last bat findsits way out. Usually 
the best procedure is to close all but 1 or 2 of the principal openings 
during the day, then wait for 2 or 3 days until the bats have learned 
to use the only entrances left them, and then close these several hours 
after dark. If any openings have been overlooked the bats will 
probably find them. It will be necessary therefore to watch the house 
closely at dusk for a few days in order to complete the bat proofing if 
any bats are seen leaving or entering. 
TO DRIVE BATS Out of a roost by a repellent is sometimes simpler 
than to bat-proof the building. This is true where the bats infest 
Bat double walls, spaces between roof and ceiling, or other 
Renellent boxed-in places easily reached from the attic but 
aes bee dificult of access from the outside. The most 
effective repellent has been found to be naphthalene flakes. This 
chemical is inexpensive and can be obtained from any drugstore. The 
bats greatly dislike the gas given off by the naphthalene and will 
leave the roost in broad daylight within a few minutes after it has been 
introduced. The flakes should be thrown liberally around or into the 
spaces occupied by the bats. Ordinarily 2 to 5 pounds are required 
for the average bat roost in dwellings. The bats will not return so 
long as a strong naphthalene odor remains, but they may return after 
several weeks. If they should do so, it would be necessary to repeat 
the application. Bats are difficult to dislodge from an old established 
