TWENTY-NINTH REPORT OF THE STATE ENTOMOLOGIST 



This area was considerably smaller than that infested during the 

 two previous years and the intensity of infestation was not so 

 great. 



There were no recorded migrations or flights of economic im- 

 portance during the 1941 season. Some small local movements 

 were observed in Pondera, Teton, and Cascade counties and some 

 light flights entered Judith Basin, Liberty, and Hill counties. 



The only movement of M. mexicanus observed in the State in 

 1942 were small localized flights from northern Yellowstone and 

 eastern Stillwater counties into the Yellowstone Valley and local 

 dispersals in Big Horn County and other areas. 



From 1938 to 1940 the grasshopper migration progressed mostly 

 in a northwest and westerly direction. Each year there was a de- 



Figure 1. Grasshopper egg beds, 1939 to 1941. 



crease in extent and degree of infestation until the Rocky Moun- 

 tains were reached in 1940. Since that time no comparable migra- 

 tions have been observed. 



It has been interesting to note, especially since 1939, that there 

 has been a marked decrease in intensity of 'hopper populations, 

 apparently due to unfavorable weather conditions, other natural 

 factors, and intensified control work. Regardless of these adverse 

 factors the numbers of 'hoppers present each year have been great 

 enough to be a serious threat to crops. It seems that the tremen- 

 dous populations that were present in 1938 and 1939 have made it 

 possible for the 'hoppers to maintain a threatening condition due 

 largely to sheer weight in numbers. 



