wade: calcium cyanide for prairie dogs 
April, ’24] 
339 
had thus literally wiped out, for the time being at least, a native and 
uncultivated plant species in three distinct localities. 
The destruction of its food plant resulted, as might be expected, disas¬ 
trously for the insect itself, and the behavior of the insect thus became 
interesting from another standpoint, namely, as illustrating the phenom¬ 
enon of a remarkably sudden appearance and disappearance of large 
numbers of what appears to be a non-migratory insect. As the feeding 
of the larvae in 1921 was insufficient to attract attention, their numbers 
that summer must have been very insignificant. And none were found 
during the summer of 1923. The appearance, subsidence and complete 
passing of the insect may thus be said to have been contracted within 
the narrow limits of a single season. 
It was the failure of its food supply that was responsible, as far as 
could be seen, for the extinction of the insect, as no disease apparently 
was present—none, certainly, in epidemic proportions—and the per¬ 
centage of insect parasitism as indicated by the rearing of large numbers 
of the insect was very small. 
THE EFFECTIVENESS OF CALCIUM CYANIDE IN THE EX¬ 
TERMINATION OF THE BLACK TAIL PRAIRIE DOG, 
CYNOMYS LUDOVICIANUS (ORD.) 
By Otis Wade, University of Missouri 
Abstract 
The efficiency of calcium cyanide as a control for prairie dogs was tested in 1922 
and 1923 in Kansas. The flake form of the chemical was used in dosages of tyf, 1, 
1 ft, and 2 ounces. The material was placed in each burrow entrance from 1 to 2 
feet below the rim. 
In three “dog towns” doses of 1, \]/ 2 , and 2 ounces were used and all entrances to 
dens closed. Total kills resulted in each instance. Eight infested areas were treated 
with 24» 1, and \ ]A ounce doses and all burrow entrances left open. In the two 
tests with 1 ounce doses total kills were obtained. Complete extermination 
resulted in one test with 1 ounce doses. In the remaining five tests where doses of 
24 to 1 ounce were used, the effectiveness varied from 90 to 99 per cent. 
The killing power of the chemical in open burrows in an important factor, since the 
closing of burrows involves considerable time and labor. 
Preliminary tests by Professor F. L. Hisaw, Kansas State Agricultural College, 
indicate that calcium cyanide might be effectively used in the eradication of the 
pocket gopher, Geomys bursarius (Shaw). Doses of 1 and 2 ounces were used. The 
dose was placed in the main run through an opening made with a trowel. After 
dosing the holes were closed. Effectiveness varied from 88 to 94 per cent. 
The use of calcium cyanide for the destruction of rodents was noted in 
a report by Professor George E .Sanders of Nova Scotia in 1921. In 
