4 MONTANA EXPERIMENT STATION BULLETIN 384 



ished to farmers. The area involved was so large, though, that great 

 numbers of grasshoppers reached maturity and migrated in the 

 fall of 1939 (figure 1) . 



AREA HEAVIiy INFESTED WITH EGGS 

 SPRING 1939 



AREA HEAVILY INFESTED WITH EGGS 

 SPRING 1940 



Figure 1. Egg infestations (Melanoplus mexicanus) in the springs of 

 1939 and 1940, resulting from the invasion of 1938. Arrows show direction 

 of flight. 



This new migration was primarily to the northwest again, and 

 flying 'hoppers invaded an area as far west at Toole, Pondera, Te- 

 ton, Chouteau, and Fergus counties. The survey in the fall of 1939 

 indicated that the area so heavily infested in the summer of that 

 year was now practically devoid of these pests, while an area in- 

 volving Phillips, Blaine, Hill, Liberty, Toole, Pondera, Teton, Chou- 

 teau, and Fergus counties which had received the migration, was 

 heavily infested with eggs. Hill County, which had an infestation of 

 83 per cent, was the most heavily infested county ever recorded in 

 the country. 



Fortunately, practically all of the eggs were laid in crop and 

 idle land, and the range did not present the problem which it did 

 in east-central Montana in the summer of 1939. The special Feder- 

 al program was again in operation during the 1940 control season 

 but was largely limited to the treatment of roadsides. The hatch 

 in the spring of 1940 was well indicated by the previous fall's sur- 

 vey, but the intensity of the hatch was not forseen. 



Migrations commensurate with those of the summers of 1938 

 and 1939 did not occur during the summer of 1940, although there 

 was a great deal of general movement. The 'hoppers were in a 



