GRASSHOPPER EGG-POD DISTRIBUTION 
7 
Table 5. —Variance in numbers of egg pods per % square foot in one 
locality in South Dakota 
Areas sampled 
Degrees of freedom 
Mean square 
Between fields. 
9 
U.16 
Between locations within the same fieid. 
490 
2 .26 
Between units within the same location . . 
500 
.20 
‘Significant at 1-percent level of probability. 
Significant at 5-percent level of probability. 
As was expected, the field-population differences were highly signifi¬ 
cant. Population variations due to locations within fields were significant, 
but the difference was not great and probably could not have been 
recognized, except for the large number of samples involved. 
It has been pointed out that in some habitats, such as small-grain 
stubble, the number of egg pods approximated fairly consistently the 
average number in all the habitats (table 1). This fact, plus the fact that 
small grain is well distributed over the northern Great Plains, suggested 
the possibility that this habitat alone might be used in conducting the 
general survey. The experimental sampling both in grainfields and in 
other common types of habitat in two central Montana counties in 1939 
seemed to indicate the reliability of such procedure. 
Further evidence on this phase of the problem was obtained from the 
10-county survey in north-central Montana in 1940. The average egg-pod 
populations for all fields, all margins, grainfields, and fields other than 
grain and their margins are given in table 6. Since field margins comprise 
Table 6 . —Mean egg pod populations per square foot for fields, margins, 
weighted fields and margins, grain-stubble fields, and fields other than 
grain and their margins in 10 counties in north-central Montana in 19^0 
County 
All 
fields 
All 
margins 
All 
fields 
and 
margins 
Grain- 
stubble 
fields 
Fields 
other than 
grain and 
their 
margins 
Blaine . 
0.59 =*= 0.07 
0.83 =*=0.08 
0.60 =*= 0.06 
0.40=*=0 
.03 
0.82 =*=0.12 
Cascade. 
.52=*= 
.07 
.65=*= 
.08 
.53=*= .06 
.41=*= 
.07 
.68=*= .11 
Chouteau. 
.46=*= 
.06 
.90=*= 
.16 
.48=*= .06 
.36=*= 
.05 
.87=*= .17 
Fergus. 
,41=t 
.06 
. 66=*= 
.14 
.42=*= .05 
.37=*= . 
.08 
.47=*= .07 
Fergus 1 . 
1.80=*= 
.16 
2.87=*= 
.77 
1.85=*= .15 
1.91=*= . 
,18 
1.40=*= .27 
Hill . 
.40=*= 
.08 
1.21=*= 
.22 
.44=*= .07 
.44=*= . 
.08 
.46=*= .18 
Judith Basin . 
. 10=*= 
.02 
.08=*= 
.03 
.10=*= .02 
.11=*= . 
.03 
.08=*= .03 
Liberty. 
.36=*= 
.05 
.68=*= 
.08 
.38=*= .04 
.36=*= . 
.05 
.53=*= .14 
Pondera. 
.77=*= 
.06 
2.70=*= 
.19 
.86=*= .05 
.77=*= . 
,06 
1.01=*= .09 
Teton. 
.58=*= 
.10 
1.87=*= 
.26 
.64=*= .09 
.48=*= . 
09 
1.20=*= .24 
Toole. 
.41=*= 
.05 
.51=*= 
.07 
.41=*= .05 
.41=*= . 
06 
,41± .07 
‘1939 survey. 
only about 5 percent of the total farm area, the averages for fields and 
for margins were given weights of 95 and 5, respectively, in obtaining 
