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SB 3 | tiv. INSECTS 
No. 117. Issued Februa 
‘nited States Department of Agriculture, — 
BUREAU OF ENTOMOLOGY, 
L. O. HOWARD, Entomologist and Chief of Bureau. a 
THE WESTERN GRASS-STEM SAWFLY. 
(Cephus occidentalis Riley and Marlatt.) 
power . 
By I. M. WEBSTER, 
In Charge of Cereal and Forage Insect Investigations, P EE: 
and 
Gro. I. REEVES, 
Special Field Agent. 
INTRODUCTION. 3 
ee : : ie 
The western grass-stem sawfly (Cephus occidentalis Riley and vat 
“ 
Marlatt), which has caused much alarm and not a little loss to the 
wheat growers of North Dakota during the season of 1909, is not by | 
any means a new insect, although this is its first appearance in the 
Fie. 1.—Western grass-stem sawfly (Cephus occidentalis) : a, Larva; b, female sawfly ; 
c, grass stem showing work. c, Enlarged: a, b, more enlarged. (From Marlatt.) ial 
United States as a serious pest. It was first observed in 1890 and h 
since been reported at intervals as feeding upon grasses an oO 
sionally upon wheat in Canada and the United States. For th 
pose of affording farmers all available inforn)aieaberela 
22045—No. 117—10 
