THE WESTERN GRASS-STEM SAWFLY. 7 



eggs appear to have hatched and at harvest time the majority of the 

 wheat stems had been bored and many were cut off at the base. 

 Careful harvesting and the use of horse rakes saved a large proportion 

 of what otherwise would have been a total loss. The infestation 

 was much more general than in 1916. 



A somewhat hasty reconnaissance was made through north-central 

 North Dakota in August, 1919, that it might be ascertained as 

 definitely as possible just how the Cephus attack was progressing. 

 A number of fields in Bottineau County were examined and found to 

 be heavily infested. Most of these had been raked after harvest and 

 it was consequently impossible to compute accurately the percentage 

 of infestation. The numerous sawfly-inhabited stubs in the drill 

 rows, however, proved the severity of the attack. It was roughly 

 estimated that about 30 per cent of the grain had gone down in most 

 of these fields as the result of Cephus work. This figure is probably 

 very conservative. 



It is conceded by many observers in that region that the injury 

 during the year 1919 was greater than during any previous year since 

 the study of this pest was begun. More fields had been seriously 

 invaded and were injured to a larger extent than had before been 

 observed. Even fields of durum wheat, hitherto believed to be 

 nearly free from fly attack, were severely injured in 1919, if the 

 statements of reliable farmers are to be accepted. The question of 

 immunity of durum wheat will be discussed later in this paper. 



It may be stated, however, that the farmers are profiting by past 

 experience and have used horserakes in stubble fields to such an 

 extent that the percentage of actual loss of grain has been reduced 

 to a small figure. The quality of grain from the fallen straw is 

 naturally somewhat below the normal, since the work of the larvse 

 in the stems produces some injury in the heads as they fill. 



Cephus was found mining wheat near Hettinger in southwestern 

 North Dakota, July 18, 1917. September 22, 1917, infested wheat 

 was found near Mott, 30 miles north of Hettinger. In October of 

 the same year many wheat fields in Towner and Cavalier Counties, in 

 northeastern North Dakota, showed heavy infestation, although dur- 

 ing the previous year it was difficult to discover more than a trace of 

 Cephus presence in the wheat in this region. None was found in the 

 vicinity of Fargo, although it doubtless occurs throughout the entire 

 Red River valley. 



A gathering of sods of Elymus canadensis sent to the writer from 

 Charleston, Mo., during the summer of 1917 contained at least one 

 larva of Cephus cinctus that had been boring the stem of this grass 

 in that region. This locality is a little south of the latitude of Pinto, 

 Utah, where this insect abounds. ■ 



