252 SCHOOL ENTOMOLOGY 



joints, but always become fixed in the plant, absorbing its 

 sap and destroying its tissues. The dark color of the leaves, 

 the absence of central stems and the s tooling out of the 

 plants are among the indications of injury in the fall or 

 winter wheat. Later many plants yellow and die. The 

 spring maggots attack the laterals, or tillers, which have 

 escaped the fall brood, so weakening them that the stems 

 break and fall before ripening and cannot be readily har- 

 vested. 



The maggots become grown in about a month, when the 

 skin shrivels and turns brown and inside it is formed the 

 pupa. This outside case composed of the larval skin is 

 known as the "puparium," and this is commonly called the 

 " flax-seed" stage from its resemblance to that seed. The 

 winter is passed in the pupal stage and the flies emerge in 

 April or May. The summer brood remains in the " flax- 

 seed" stage in the stubble during the late summer and the 

 flies emerge when the first wheat is planted in the fall. 



The principal means of control is by the late planting 

 of wheat in the fall. The flies appear within about a week 

 and then disappear and if planting be delayed so that the 

 wheat will not be up until after that time, there will be but 

 little injury. Dry weather in late summer and early fall 

 delays the appearance of the flies and the farther south, the 

 later they appear. In average seasons it will probably be 

 found safe to sow wheat in the latitude of northern 

 Michigan soon after September 1st; in southern Michigan 

 and northern Ohio about September 20th; in southern 

 Ohio after the first week in October; in Kentucky and 

 Tennessee, October 10th to 20th, and in Georgia and South 

 Carolina, October 25th to November 15th. The exact time 

 will also depend upon the altitude, every 100 feet of alti- 

 tude making the date about one day earlier. As the infesta- 



