JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 17 
light scattering movement occurs during the rest of the day. When 
the gas and mechanical barriers are combined the log, as in the ditch- 
log barrier, can be kept moving thruout the morning when but few 
bugs are moving, and then the gas barrier laid down in the afternoon 
when heavy movement starts. 
However, Missouri farmers prefer either to fight all the time with 
the ditch-log or to use the gas alone. Only a few reported using the 
combined barriers. 
In our tests the broad, rounded furrow with one pound of calcium 
cyanide to sixty feet remained effective for only two or three hours 
and did not prove entirely effective thruout the afternoon migration. 
The type of furrow used most in Missouri was a plowed furrow with 
the dirt thrown toward the wheat stubble and the side next to the 
com as nearly as possible a vertical wall. This is the type of furrow 
most farmers make and we have found it to be the most effective. 
This is probably due to the fact that it provides the best protection 
against the drifting of the gas and the concentrating of gas at the foot 
of the vertical wall. The vertical wall is also an effective barrier up 
which the bugs, already weakened by the gas, are unable to climb. 
In such a furrow one pound of calcium cyanide flakes to each sixty feet 
applied in the early afternoon proved effective in preventing bugs cross¬ 
ing for the rest of the day. This is the dosage and type of furrow and 
method of application which gave us best results this summer. Like¬ 
wise, this is the type of barrier used by most of the farmers in the state. 
Our tests were made in different counties in the northern part of the 
state thruout the migration period. The migration was later than 
normal and more drawn out than usual which made the use of any 
type of barrier more difficult than under normal conditions. We 
believe, therefore, that in a normal season with a heavy active migration 
of bugs, the gas barrier would have-worked more rapidly, cleaned up 
the bugs in fewer days and thus proven more effective and cheaper. 
Still our results last summer were highly satisfactory and the farmers 
using the material were pleased with their results as the following sum¬ 
mary of their reports will show. 
Sixty-five questionnaires were sent out to Missouri farmers, who 
used calcium cyanide for chinch bug control, and thirty-three replied. 
Of these, twenty used the material in a furrow and all reported success 
even tho four used less than one pound to sixty feet of barrier a day. 
Thirteen used other methods and all but one of these reported satisfac¬ 
tory results. Of those following directions only one considered the 
