8 BULLETIX 841, U. S. DEPARTMENT OF AGRICULTURE. 
Roughly speaking, so far as is now known, the sawfly inhabits an 
area bounded on the north by a line far into Canada: on the east by 
the Mississippi River, or probably a little east of that: on the south 
by latitude 36°: and by the Pacific Ocean on the west. 
From the foregoing brief summary of its history it will be seen that 
Cephas cinctus is distributed over an immense territory and that it 
constitutes a potential menace to the small grains throughout this 
vast area. As the acreage of native grasses is decreased from year 
to year by the bringing of wild lands under the plow, pests such as 
the sawfly will be forced to depend in an increasingly large measure 
upon the small grains and other products of the farms. On this 
account the injury caused by these formerly harmless insects bids 
fair to increase steadily. In the past the numbers of grass-feeding 
insects such as the one considered in this paper have been governed 
mainly by the supply of food plants. A dry summer that retarded 
the growth of long-stemmed grasses would automatically reduce the 
numbers of the insects that lived within these grass stems and perhaps 
bring certain species to the point of extinction. It is easy to see 
how seasonal fluctuations in vegetation would, to a large extent, 
either multiply or diminish the numbers of these insects. 
Then again, the farmer, by introducing fields of grain into a region 
previously uncultivated, brings in conditions unknown before and 
invites the attack of these and other formerly harmless insects, 
making it possible for them to become a menace to his future. Such 
a study of life history as has been attempted in this paper is urgently 
necessary in order that control measures may be undertaken suc- 
cessfully when such insects become pests. 
FOOD PLANTS 
The various species of Agropyron and Elyrnus, genera both of 
which are well represented in the West, appear to have been the 
original hosts of the larvae. Since their feeding habits have been 
modified by changing agricultural conditions, the list of their present 
host plants, so far as known, stands as follows: 
Elyrnus canadensis Agropyron occidentale Calamagrostis spp. 
Elyrnus condcnsatus Agropyron caninum Festuca sp. 
Agropyron tenerum Hordeum jubatum Ulieat 
Agropyron richardsoni Bromus inermis Durum 
Agropyron smith.it Phleum pratense Spelt 
Agropyron repens Deschapsia sp. Rye 
Barley probably should be added to this list. 
Since the larva is wholly unable to move from one stem to another, 
it is very obvious that the host stem must be large enough to afford 
both shelter and food during its entire growing period. Hence only 
the larger-stemmed grasses can be mined successfully by the Cephus 
