37 
insects attain a length of nearly an inch, are usvally dull or dirty 
whitish in color, with the head marked with brown. Some of them 
are also marked with brown stripes or spots along the side of the 
body. They occur, as a rule, 
singly, and are rarely in sufli- 
cient numbers to be of any 
economic importance. 
GRASS SAWEFLY ( Pachynematus 
extensicornis Nort.). 
A more important species is 
the insect bearing the scien- 
tific name of Pachynematus 
eatensicornis Nort. (fig. 25), a 
grass sawfly about the size of ot, 
a common house fly, which Fie. 24.—Leaf-feeding saw fly (Dolerus arvensis): female— 
occurs throughout the North- enlarged (author’s illustration). 
ern States east of the Rocky Mountains. The eggs of this insect are 
inserted in rows along the edge of the blades of wheat, or more com- 
monly in grasses, and the larvee hatching from these feed on the leaves 


Fie. 25.—Grass sawfly (Pachynematus extensicornis): a, eggs in wheat blades; b, young larve; c, full- 
grown larva; d, cocoon from which adult has issued; e, male; /, female—a and b, vatural size; c-f, 
enlarged (author’s illustration). 
more or less gregariously while young. As they become full grown 
they separate and become practically solitary feeders, as in the case of 
the larvee of Dolerus. They may be distinguished from the latter, 
132 
