12 MONTANA EXPERIMENT STATION BULLETIN 408 



tains into crops in the Owl Creek and Sioux Pass areas in Big 

 Horn County. 



In 1942 it was necessary to carry on Mormon cricket control 

 work in only two counties in the State. These infestations were 

 located on Owl Creek and Sioux Pass east of Lodge Grass, on Beau- 

 vais Creek in Big Horn County and in the southeastern corner of 

 Yellowstone County east of Pryor Creek. 



To prevent reinfestation of the lower lands it was thought that 

 a control program would be needed in Beaverhead County west of 

 Monida, in the vicinity of Beaver. Big Beaver, and Poison creeks, 

 near the Montana-Idaho State line. The 1941 campaign was suc- 

 cessful to the extent that the only crickets left in this area were on 

 the Continental Divide at about 7,800 feet elevation. In the fall 

 of 1941 this area was visited and large numbers of crickets were 

 observed. Again in the early summer of 1942 the area was scouted 

 and only an occasional cricket could be found so that control work 

 was not necessary. Since it seemed unusual that there were no 

 crickets where such large numbers of adults had been found the 

 previous fall, another investigation was made in September of 

 1942. It was found that there are large numbers of eggs in the 

 ground and that this is apparently a "hold-over" area where the 

 eggs hatch in two years. 



TABLE 4. SUMMARY OF MORMON CRICKET CONTROL, 1941 and 1942 



1941 1942 



Crop savings $87,290 $38,750 



Crop losses $2,680 $1,200 



Crop acres protected 46,160 22,038 



Acres injured 4,635 890 



Crop acres infested 172,800 14,196 



Range acres infested 1,007,340 569,758 



Total infested 1,180,140 583,954 



Acres dusted 3,757 912 



Acres baited 24,419 6,873 



Pounds mixed dust 17,396 5,945 



Pounds mixed bait (dry weight) 197,043 110,706 



In 1939 the first discovery of the hold-over phenomenon was 

 made in the Big Horn Mountains in Wyoming. At this time it was 

 found that Mormon cricket eggs laid at high altitudes often require 

 two years to hatch. Ordinarily Mormon cricket eggs laid in the 

 summer or fall hatch the next spring. In a "hold-over" area, how- 

 ever, they remain in the ground for two winters and a summer be- 

 fore hatching. 



From the eggs that were collected in Beaverhead County in 

 the fall of 1942 it was found that 60 per cent were viable and con- 

 tained well developed embryos, 10 per cent were not viable, and 

 30 per cent had been parasitized by Sparaison pilosum. 



On investigation of the eggs it was also found that parasites 



