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greatest in recent history, which occurred in July 1938 in the northern 
Great Plains area. These developed from large reservoirs of this species 
which hatched out in numbers ranging from 1,000 to 10,000 per square yard 
in idle and weedy range lands adjacent to cropped fields. These reservoirs 
were located in large areas of north-central South Dakota, east of the 
Missouri River, such areas continuing northward into North Dakota and thence 
diagonally northwestward across that State and in other areas in the south- 
western part of North Dakota. The flights were to the northeast, north, 
northwest, and some south?/est, infesting new territory in the Red River 
Valley of Minnesota and North Dakota, parts of northern North Dakota, a re- 
infestation in the Mandan to Dickinson areas, including the Bad Lands, the 
eastern half of Montana, which had no serious infestation to begin with; a 
large part of extreme eastern Wyoming; and the Black Hills area of western 
South Dakota* 
Nymphal surveys were conducted in the northeastern quarter of South 
Dakota from May 7 to July 2, inclusive. The high spots of the trend of the 
grasshopper populations for fields and field margins were as follows; 
Date : Population found in — 
{ Field ; Field margin 
; Number : Number 
« t 
May 7 : 5 : 35 
June 4 j 192 ; 260 
June 18 ; 190 : 245 
jjuly 2 ; 73 ; 119 
These are averages of all the observations made in the northeastern 
quarter in which populations as high as 1,500 per square yard in the field 
were recorded in some places between June 4 and June 18, There was a general 
exodus of M. mexicanus from this area the last week of June and the first 
week of July, This is evidenced in the figures from the nymphal survey 
which show a sharp decrease of population between June 18 and July 2. This 
would have been more marked if it had not been for Melanoplus dif ferentialis 
coming in about this time and holding up the populations to a certain extent. 
A similar population trend in eastern Montana was as follows: 
Date ; Population found in — 
; Field ; Field margin 
; Number : Number 
May 28 ; 10 : 83 
June 4 : 18 ; 44 
June 18 : 22 ; 80 
July 9 : 60 : 76 
