142 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



straw has hardened. By October, in the Middle West, though 

 earlier in the South, they pass into the pupal stage, in which, as a 

 rule, they remain until early spring, whereupon they develop to 

 adults and gnaw their way out." In the Northwest, where both 

 winter and spring wheat are grown, the injury is particularly 

 severe to spring wheat, as the adults of the second generation from 

 winter wheat oviposit upon it while it is still young and ruin it in 

 much the same way as the first generation does on the winter 

 wheat in spring. Volunteer plants which carry the pest over 

 winter have the same effect in increasing the injury to spring 

 wheat. 



Control. A rotation of crops which will eliminate the growing 

 of wheat two years in succession on the same land is by all means 

 the most successful and practicable means of control. The adults 

 of the first generation are very small and largely wingless; they are 

 unable to migrate far, so that rotation is exceedingly efficacious, 

 though it should be planned so that wheat is not planted next to 

 stubble land, for the edge will become infested by the first genera- 

 tion, and the second generation will then become distributed 

 throughout the field: The burning of stubble and outstanding 

 straw will be advantageous wherever practicable. Clean fallow- 

 ing in early summer and the abandonment of spring-wheat culture 

 will reduce injury in the Northwest. 



Wheat Saw-flies * 



Several species of saw-fly larvae sometimes feed on the leaves 

 and rarely on the heads of wheat, but seldom do serious injury. 

 Dolerus arvensis Say and Dolerus collaris Say have both been 

 reared upon wheat from Ohio and New Jersey, though both species 

 occur throughout the United States and southern Canada east of 

 the Rockies. The adult flies " are comparatively large, robust in- 

 sects, of a dull black or bluish color, varied w r ith yellow or reddish." 

 " The larvae are quite uniform in color and general characteristics. 

 They have twenty-two legs, are cylindrical, and generally of a 



