340 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
his experiments the material was used with success in the control of a 
species of ground squirrel commonly referred to in that region as a 
“gopher.” 
Since calcium cyanide is receiving considerable publicity and is being 
strongly recommended by some as an efficient control for various 
noxious rodents, it seems desirable to report the results obtained with 
this material in tests made on the prairie dog in Kansas. These tests 
for the control of prairie dogs were made by the writer in May and 
August 1922 and April 1923. 
The flake form of calcium cyanide was used throughout these ex¬ 
periments. The doses were placed down in the burrow entrances 
from one to two feet from the rim. 
Except in three tests, all entrances to the burrows were left open 
after the calcium cyanide had been administered. This was done 
because it was thought if the material did not prove effective without 
closing all entrances, which is a slow laborious process, it would not be 
superior to methods already in use and it was the labor and attendant 
cost we wished to eliminate if possible. 
The following data give the results of the first experiment: 
Date 
Area 
Dosage 
Entrances 
Results 
May 4, 1922 
40 burrows 
2 ounces 
Closed 
Total kill 
May 5, 1922 
.58 
11 
lA “ 
l L 
u 1 4 
May 5, 1922 
157 
i < 
l 
4 i 
i i i ( 
May 5, 1922 
107 
i i 
lA “ 
Open 
it 4 4 
Several inspections of the treated areas were made in May and June 
and a final inspection July 20. Not a living prairie dog could be dis¬ 
covered. A number of dead burrowing owls were noted in the entrances 
of open dens. 
The second experiment was conducted August 3 with the following 
results. 
Date Area Dosage Entrances Results 
Aug. 3, 1922 88 Burrows A to 1 ounce Open About 98% kill 
Aug. 3, 1922 64 “ lj^ ounce “ Total kill 
August 4 in the area treated with the smaller dose, three live dogs 
were seen and fresh work around the entrances of two dens was ob¬ 
served. The supply of calcium cyanide being exhausted these two live 
burrows were treated with heavy doses of carbon bisulfide to insure the 
death of the inmates. In the second town where more than one hundred 
prairie dogs were seen the previous day, there was no sign of life and 
the town appeared deserted. Eight dead burrowing owls were found 
