^ 13 ?£Z 
3 
V GRASSHOPPER EGG-POD DISTRIBUTION 
.miles wide and 4 miles long, in Montana, North Dakota, and South 
Dakota. One of the main objectives was to test and improve grasshopper- 
survey methods. 
In the egg surveys made during the earlier years of the studies, 10 or 
more 1-square-foot samples were taken on every quarter section of land. 
By 1938 doubt had arisen as to whether the number of samples taken on 
the areas was too few or too many, and whether taking a fixed number 
of samples per unit area is the most accurate way of determining mean 
egg-pod populations in the various crops and habitats. That the personnel 
charged with conducting the general surveys were also in doubt regarding 
the adequacy of sampling is evident from the changes made in the sam¬ 
pling instructions given the surveyors. To determine the dependability 
of sampling procedure several counties were surveyed in sufficient detail 
to obtain data for statistical analysis. 
The first special intensive egg survey was conducted in the fall of 1939 
in Fergus and Judith Basin Counties, in north-central Montana. With 
the aid of one member of the general survey staff, 200 fields were exam¬ 
ined in 2 counties, which were treated as a single unit. In 1940, with the 
assistance of survey personnel supplied by the Division of Grasshopper 
Control and the Montana State entomologist, special egg surveys were 
conducted in 10 counties in north-central Montana, 70 fields in each 
county being sampled. The last of the special egg surveys was conducted 
in Davison and Brown Counties, South Dakota, in 1942. After the special 
county egg surveys were completed, the data from them and from the 
study areas were analyzed by methods developed along the lines shown 
by Snedecor. 4 
EGG-POD DISTRIBUTION 
In Relation to Types of Vegetation Habitats 
In any adequate study of sampling methods the distribution of the egg 
pods among the different habitats must be considered. Although it has 
been common knowledge for years that grasshoppers are selective in their 
egg-laying habits, accurate comparisons of the egg populations in habi¬ 
tats were lacking. Intensive studies were made, therefore, of egg-pod 
distribution in fields and field margins. 
Records of egg populations in different plant associations on the 
northern Great Plains study areas for the 8-year period 1936-43 are 
summarized in table 1. It can readily be seen that some habitats, such 
as field margins and idle land, contain greater egg concentrations than 
others. As to egg-pod category, the first four habitats listed could be 
classed as high, the next four as medium, and the last five as low. Plowed 
and fallowed lands, not listed in the table, had practically no egg pods. 
Although the position of each habitat varied somewhat from year to 
year, as compared with its 8-year average, most of the variations were 
not great enough to change a habitat from one category to another. This 
tendency to remain in about the same relative position from year to year 
led to the idea that a single habitat might be used in carrying on the 
general survey. 
4 Snedecor, G. W. statistical methods, Ed. 3, 422 pp., Ames, Iowa. 1940. 
