THIRTIETH REPORT OF THE STATE ENTOMOLOGIST 



15 



WHEAT STEM SAWFLY (Cephus Cinctus Norton) 



This little wasp, which has been developing slowly in num- 

 bers for the past decade, appeared in large numbers and over 

 a considerable area during the 1943 season, and increased its area 

 of infestation in 1944. To recapitulate briefly its history, it was 

 first discovered in wild grasses and transferred its interest to 

 small grains when these were planted in large acreages in the 

 northern part of the Great Plains Area. Apparently the first in- 

 jury to wheat was noted by James Fletcher in 1896 from specimens 

 sent in to him from Souris, Manitoba. First definite injury to this 

 crop in the United States was noted in 1909 in northern North 

 Dakota. This injury became intense about 1916 and continued for 

 some years after which the infestation receded. Montana is now 

 suffering its first recorded major outbreak of this insect in small 



^.W : ] KNOWN INFESTATIONS 19*3 

 Y///A ADDITIONAL INFESTATIONS I94H 

 Figure 4. Distribution of wheat stem sawfly. 



grains. In 1943 the infestation was most injurious in two separate 

 areas in the State. To the west it was abundant in grains in east- 

 ern Glacier, western Toole, central Pondera, and northern Teton 

 counties. To the east it occurred in parts of Blaine, Valley, Phil- 

 lips, Daniels, Sheridan, Roosevelt, and Richland counties. During 

 the 1944 season the western infestation did not show any striking 

 increase in area — in some areas there was an apparent but slight 

 reduc f i°n in mtensitv. The eastern area, however, developed a 



