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important, and in mountain valleys the same is true of Camnula pellucida . 
Field margins are not such important sources of infestation in Montana as 
they are in other States, where M. b.ivittatus , M. differential i s, or _C. 
pellucida often occur in outbreak numbers. Therefore the true current index 
to grasshopper conditions in Montana- is probably the relative numbers of 
M. mexicanu s found in small gra-in, idle land, or range land. 
The table for Montana shows decidedly smaller numbers of all species 
in all habitats in 1937, as compared with 1536. Unprecedented flights 
of Melanoplus mexicanus from the Dakotas in July 1938 doubled or tripled 
the average M. mexicanus population in crops and increased it sixfold on 
the range land. Although the infestations shifted by flights in 1939 from 
eastern to north-central Montana,, the averages for M. mexicanus for the 
State remained about the same. 
The data indicate that in 1940 decidedly smaller numbers of all 
species occurred in all environments, and that in 1941 slightly larger 
numbers occurred in the small-grain crop, with greater increases in idle 
land and range land. The exceptional rise in numbers in idle land in 1941 
may be due to the fact that idle land was surveyed on only two of the five 
Montana areas. The infestations in these two areas were comparatively heavy 
hence they are not truly representative of the infestation in the idle 
lands of the State as a whole. 
The surveys for the 6 years do not reflect consistently the numbers 
of grasshoppers in the minor habitats from year to year. Four of the a,reas 
surveyed in 1940 and known to be lightly infested in 1941 were not included 
in the 1941 survey, A revision of the project made it necessary to omit 
them and retain only those having the heaviest infestations and the most 
important grasshopper history. Thus there probably was not the general in- 
crease in population in 1941 that the figures in the table indicate. 
Because of" differences in crop, soil, and climatic conditions, 
Nebraska was divided into eastern and western parts, making the division 
along the western boundaries of Boyd, Holt, Garfield, Valley, Sherman, 
Buffalo, Phelps, and 'Harlan Counties. 
The eastern part includes about two-fifths of the State and has 
more intensive farming and a greater amount of rainfall and native vege- 
tation than the western part. Corn is the major crop, with small grains 
second., and with alfalfa relatively more important than in the western 
part of the State. Pastures are small. Melanoplus differential is is 
probably the principal economic species here, being the most important 
one in corn, sorghum, and alfalfa areas. M. mexicanus and M, biv it tutus 
are of secondary importance. 
In the western three— fifths of the State the sand-hill section 
comprises over half the area., with much open range land and waste land 
throughout. Melanoplus bi-vittatus replaces M. differential is in part, 
and M. mexicanus is the dominant species. 
