12 MONTANA EXPERIMENT STATION BULLETIN 366 



conditions in the northeastern corner of the State seriously af- 

 fected the campaign in that area. Most of the State suffered 

 from lack of rainfall throughout May, reducing crop prospects 

 and delaying control work. Total losses attributable to grass- 

 hoppers in 1937 amounted to $2,196,420.00. Savings, nevertheless, 

 amounted to $1,385,642. The campaign cost $62,753.37, and the 

 savings per dollar spent were $22.08. 



for 1938.— The autumn survey in 1937 indicated a general 

 reduction in potential injury throughout the State with the ex- 

 ception of the eastern border counties and a few small areas in 

 the center of the State. This prediction was borne out by the 

 resulting populations which appeared during the first half of 

 the season. One bad area in the west, involving parts of Lake, 

 Sanders, and Missoula counties, developed without warning, and 

 a considerable amount of control work was carried on in the 

 northeastern counties bordering North Dakota. The bad areas 

 were reasonably well under control by the first of July, and at 

 that time it appeared that there would be less injury from these 

 pests than for several years past. The final picture, however, 

 was very different. 



The Migrations of July, 1938 



On the first of July, crop prospects throughout the most of 

 Montana were better than they had been for a decade. On that 

 day, however, Wibaux, Carter, and Fallon counties were in- 

 vaded by hordes of grasshoppers from the southeast. The species 

 involved was the lesser migratory locust, Melanoplus mexicanus 

 Sauss. Where the "native" grasshoppers had been from 2 to 15 

 per square yard, the migrants increased the population without 

 warning to from 40 to 500 per square yard. By the third of July, 

 they covered all or a part of Carter, Powder River, Custer, 

 Prairie, Dawson, Wibaux, and Fallon counties. From the 4th to 

 the 9th temperatures were generally below 80° and there was 

 little migration. By the 10th, parts of Rosebud, Garfield, Mc- 

 Cone, and Richland counties were invaded. Winds were from 

 the northwest on the 12th and 13th, but by the 16th they had 

 continued into parts of Treasure, Petroleum, Phillips, Valley, 

 Daniels, Roosevelt, and Sheridan counties, and on the 17th they 

 appeared in the vicinity of Turner in Blaine County. 



