April, ’24] HASEMAN & BRO MLEY: CHINCH BUG AND CALCIUM CYANIDE 325 
earlier recommendations on chinch bug control have failed to properly 
control the pest in some localities in recent years is unquestioned. 
How much of this has been due to lack of cooperation on the part of 
the farmer, we shall not attempt to estimate. However, it is true that 
for the past several years this pest has continued to extract its annual 
toll in the com belt. Our failure to hold the pest is either due to 
ineffective remedies or inability to get the farmers interested in applying 
them thoroly. In either case it seems wise that we attempt to find 
some new and more effective line of attacks. The psychology of some¬ 
thing new against the chinch bug is not to be overlooked, when dealing 
with chinch bug afflicted farmers. This is especially true if the new 
recommendation proves both effective and practical. 
With these general observations we shall proceed to briefly describe 
the use of calcium cyanide for the control of chinch bugs in Missouri. 
Much remains to be found out about this new chemical as an insecticide 
but we have gone far enough to feel sure that it will play an important 
part in future chinch bug campaigns. 
Calcium Cyanide 
Calcium cyanide unlike potassium and sodium cyanide is a com¬ 
paratively new chemical. It has been used successfully for a few years 
as a fumigant in the tunnels of rodents. George E. Sanders was the 
first to take special note of this chemical as an insecticide and he interested 
others in testing it. Flint made some preliminary tests with the material 
on chinch bugs in the fall of 1922. During the summer of 1923 the 
material was used on chinch bugs in Indiana, Illinois, Missouri, Kansas 
and Oklahoma in an experimental way and also quite extensively in 
practical field control in Missouri. 
Calcium cyanide reacts with atmospheric water vapor, giving off 
hydrocyanic acid gas that makes this new chemical valuable as a bar¬ 
rier to the migrating chinch bugs. 
Tests on Rate of Emission of Gas 
At the outset laboratory and field tests were made to determine the 
rate and duration of the emission of gas. The influence of 
moisture, temperature and wind were studied. In these preliminary 
experiments only adult bugs were available for use at Columbia, Mis¬ 
souri. In order to make field tests using the immature bugs, the junior 
author was sent to Oklahoma for several days work. The purpose of 
these tests was to arrive at some definite conclusions regarding dosage 
and method of laying down the chemical as a barrier before wheat 
harvest and chinch bug migration began. 
