“ 79 
With, com, sorghums, winter wheat, and rye comprising 59 percent 
of the total land cropped in Nebraska as a whole, margins of fields, to- 
gether with alfalfa and. small pastures, "become a chief source of infesta- 
tion. In western Nebraska the trend of population for Delano pi us mexicanus , 
M. bivittatus , and M. differential is has been downward in practically all 
important environments since 1939, whereas in the eastern part the reverse 
has been true. The decided increase of M. mexicanus in small grain, le- 
gumes, field margins, and. pastures agrees with known increases in the same 
habitats in western Iowa, which adjoins. Ae ole plus turnbullii became a 
dominant species along the field margins in western Nebraska in 194-0 and 
1941 and in eastern Nebraska, in 1940 and was still important there in 1941. 
The total populations for all species may be exaggerated in the 1941 sur- 
veys, as only 4 areas were surveyed — Albion and Kearney, in the e a. stern 
part, and Chadron and Bridgeport in the western. The data are very limited. 
In the eastern part a greater normal rainfall tends to inhibit grasshopper 
increase; hence infestations in that area may not develop their potential- 
ities unless the growing season is abnormally dry. 
NORTH DAKOTA 
As to grasshopper habitats, the western two- thirds of N 0 rth Dakota 
is much like eastern Montana. Molano.plus mexicanus is the most important 
species, but M. bivittatus here becomes of greater importance than in- 
Montana, and at times M. different ialis ' becomes the dominant species in 
the area extending from Dickinson to Mandan. In the northern part Camnula 
pellucida has also been of local importance. 
In the eastern third of North Dakota the soil is blacker and richer 
and there is more rainfall and moreintensif ied farming than in the western 
part. More corn and legumes are raised and native vegetation is more lush, 
with tall grasses and weeds along the field margins. There is less of past- 
ure and other grassland. Hero M'elanoplu s bivittatus , M. mexicanus , and 
Camnula pellucida have at various times occurred in outbreak numbers. Much 
of this area, is designated as the Red ' River Valley. The division between 
eastern and western North Dakota was made at the western boundaries of 
Cavalier, Ramsey, Eddy, Faster, Stutsman, La Moure, and Dickey Counties. 
This places all of the central part of the State in the western division, 
leaving only a third of the State in the eastern division. This was done 
in order that the latter section would be limited largely to the Rod River 
Valley and the. 20- inch rain belt. 
Most of the severe grasshopper outbreaks have been limited to the 
western two- thirds of the State, and there are no records of collections 
made in the eastern third for the years 1936 and 1937, although a limited 
general survey was made there. 
As a result of the unprecedented flights of Ilelanoplus mexicanus 
into North Dakota from South Eukota in 1938, the adult populations in 
western North Dakota were increasingly higher in 1938 and 1939 than in 
1936 and 1937. From 1938 to 1939 there was a big decrease in numbers of 
Mm. m exicanus in corn, sorghums, and grassland, which are among the habi- 
tats least attractive to this species, although the more favored habitats. 
