ELIMINATING BATS FROM BUILDINGS 5 
roost, and the persistence of their characteristic odor ts likely to attract 
other bats later on. For this reason bat proofing, though more 
difficult, is a much more desirable control method than the use of the 
naphthalene. 
Kitiine the bats by fumigation is possible, although there are 
serious objections to the use of a poison gas in an occupied dwelling, 
ee aes and this method is not recommended except as a last 
Bat resort, after other means have failed. Destruction 
oF eee of the bats is usually undertaken when bat proofing is 
impracticable because of the cost and the difficulty of reaching some 
of the roosting places with a repellent. This condition means that 
it will not be possible to reach and remove the carcasses, the decom- 
position of which will for a time add to the obnoxious odors associated 
with a bat roost. It also means that the openings through which the 
bats had gained entrance to their roost must remain open, and then 
the characteristic bat odor will long remain an invitation to other 
bats to reestablish the roost. 
The destruction of the bats by fumigation can best be accom- 
plished by use of hydrocyanic acid gas, which can be generated and 
applied by several methods. The gas is highly effective, but as it 
is also extremely poisonous to human beings, it should not be used 
without full knowledge of the dangers involved and of the precaus 
tions to be taken. 
When spaces between walls are occupied by bats, they can often 
be reached from the outside by loosening boards or siding or by 
boring a hole with a brace and bit. Into such openings the nozzle 
of a dust pump may be inserted and calcium cyanide dust blown into 
the cavity. Calcium cyanide rapidly generates hydrocyanic acid 
gas by combining with the moisture in the air. The quantity of 
dust needed will depend on the size of the cavity to be filled, but in 
the average residence a pound or two of dust will usually be ample 
for treating small enclosed spaces between double wallsand between 
a ceiling and the floor above. The dust-pump method should not 
be used from the inside. The house should be vacated before cal- 
cium cyanide is used and should not again be entered until aired for 
several hours after the gassing. 
In many cases the more practical treatment would be to fumigate 
the entire attic, or even the entire building, which would allow the 
gas to penetrate into all openings and insure the destruction of all 
animal life in the building. Farmers’ Bulletin 1670, Hydrocyanic 
Acid Gas as a Fumigant, gives full instructions for fumigating 
buildings for destroying household insects, and the procedure recom- 
mended is also applicable in the destruction of bats. In general, 
when fumigation for the destruction of bats is found necessary, 
the work should be entrusted to an experienced operator. 
U.S. GOVERNMENT PRINTING OFFICE: 1935 
For sale by the Superintendent of Documents, Washington, D. C. - - - - - - Price 5 cents 
