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 sawny-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 
i mmu nity 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 larvae 
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 ductus 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. 
