& + 
states that in a field of wheat at Aweme, Manitoba, 75 per cent of the 
infested stems collapsed before harvest, but we observed a field at 
Kulm, N. Dak., to have only 6 per cent of the injured straws broken. 
The native grasses do not collapse when attacked by this insect and it 
is possible that some stiff-stemmed wheats may stand up better than 
other varieties. This is an advantage to the farmer in preventing 
total loss of the affected heads, but a disadvantage if it prevents 
him from detecting the cause and extent of a serious shrinkage of 
the kernels. 
The damage has been confined heretofore to the edges of fields 
bordered by grass lands or roadsides. Ma. Criddle7 states that 50 
per cent of the stand is infested for a distance of 100 feet into the 
fields, and that the damage is apparent to a lesser extent throughout 
the crop. He also states that the insect seeks wheat only when it 
fails to find enough flowering stems of grasses in which to deposit 
its eggs. Recent reports from North ,Dakota indicate that the injury 
may be more general than heretofore and suggest that the insect has 
probably adapted its habits to conform to the farm methods of that 
region so that it no longer depends upon native grasses but breeds 
throughout the fields, at once distributing the damage more evenly 
and increasing its capacity for harm. <A pest which can take advan- 
tage of wild food plants and yet be independent of them is far more 
dangerous than one which can feed only upon wheat or one which 
requires both wheat and a native grass. 
FOOD PLANTS. 
This sawfly is a native insect which has learned to attack wheat and, 
according to Mr. Criddle, rye also, since these have taken the place 
of its native food plants—quack grass and wheat grass (Agropyron), 
brome grass (Bromus), rye grass (Elymus), and timothy (Phleum). 
It was especially abundant in Agropyron along railroad embank- 
ments in North Dakota in 1905 and 1906, so that in many clumps 
of this grass one-half of the heads were prematurely whitened. 
DESCRIPTION. 
The larva (fig. 1, @) is about three-fifths of an inch long and one- 
eighth as wide, slightly larger near the head, and tapering toward 
the tail, which ends in a small, blunt, upturned, brown tubercle. The 
body is yellowish white; the head, a spot on the back of the neck, 
rings on the palpi, the tips of the paired cerci, and the sete on the 
last segment, are pale yellow; the margin of the cheeks and of the 
antennal segments, a faint streak on each cheek through the eve, the 
mandibles, the stigmata, and the median anal tubercle, are mahogany 
4 Toe. cit. 
(Cin wal 
