INSECTS INJURIOUS TO SMALL GRAINS 



129 



Other species of saw-flies feed on the leaves and even on the 

 heads of wheat. They, like the stem-borers, are rarely abundant 



enough to be trouble- 

 some. Among these are 

 two species called merely 

 wheat saw-flies (Dolerus 

 arvensis Say and Dolerus 

 collaris Say). These 

 species occur throughout 

 the United States and 

 southern Canada, east of 

 the Rockies. These saw- 

 flies are fairly large, com- 

 pared with the ones pre- 



'I 14O i * / ' r / ' -^ ( * 1 1* 1 ' I "* 1 



Say): female much enlarged. (After Riley viously discussed. Ihe 

 and Marlatt, U. S. Dept. Agr.) adults appear as dull 



black or bluish four-winged flies, marked inconspicuously with 



FIG. 111. The grass saw-fly (Pachynematus extensicornis Norton): a, a, eggs 

 on wheat-blade; 6, young larvae; c, full-grown larva; d, cocoon from 

 which adult has emerged; e, /, adult insects e, male;/, female, a and 

 6, natural size; c-f, enlarged. (After Riley and Marlatt, U. S. Dept. Agr.) 



