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There was an increase in average populations which was more marked- 
in a study of' the individual observations where counts of 200 and 300 per 
square yard were common in fields having only 5 per square yard before the 
grasshoppers flew in. H. B, Mills, State entomologist of Montana, has 
described the migrations of Li. mexicanus into Montana in his report, 
"Montana Insect Pests for 1937 and 1938" (Rpt, 27, State Ent. Bull. Mo. 368, 
pp. 12-16, Jan. 1939'). This description is based on observations made by 
Federal and State men connected with the grasshopper-control program who 
were cnecking on the flights. In this article Mills has mapped the spread 
of lu_ mexicanus into eastern Montana. Beginning with July 1 in Wibaux, 
Fallon, and Carter Counties, the crest of the migration moved progressively 
westward and. northwestward until by July 17 it reached into Blaine, Petroleum, 
and Treasure Counties, or a line north and south 200 miles west of the 
eastern State boundary. Here the flights termina.ted and it is in this 
area that egg deposition was the heaviest. These migrations also extended 
north into Saskatchewan. 
The small farms in the Black Hills of South Dakota also received 
their share of these migrants. This was evidenced by the high egg counts 
in this area. All of the eastern counties in Wyoming were also on the re- 
ceiving end of these migrations. In Goshen County north of Torrington the 
area inva.ded by the migration of M. mexicanus shows egg counts of 4 to 16 
pods per square foot in the field and 1 field- of 29 pods per square foot. 
Unless conditions unfavorable to grasshopper development- occur, this area 
in 1939 will probably produce as. heavy populations as those which developed 
in north-central and eastern South Dakota in 1938. If this happens then 
large flights of M. mexicanus can be expected to develop in this area. 
The other area where heavy egg deposition occurred from these flights 
was the reinfested section in the region north and south of a line from 
Mandan to Medofa, N* Dak. Egg predators reduced the number of good eggs 
25 to 75 percent, otherwise this would have been the most heavily infested 
of all the areas. Viable egg pod counts here still run 4 to 16 per square 
foot. 
Egg Survey of Range and Idle Land in 
the Mel ano plus mexicanus Area Proper 
As a part of the fall gras shopper- egg survey ih the Northern Great 
Plains area infested by M, mexicanus , a separate survey Was made of the 
range and idle land. In this survey only egg pods of this species were 
considered insofar as it was possible to determine their identity by 
superficial inspection. The States in which surveys were made were 
Montana, Worth Dakota, South Dakota, Wyoming, and the western part of 
Nebraska. Only a few examinations were made in Nebraska. The survey was 
divided into two parts, one being done as a special survey made by R. A. 
Roberts and the other as a part of the regular crop survey made by the 
district surveyors. Mr, Roberts has written up his report as a separate 
project. for comparison with the reports of the district surveyors. 
