time; thus, owing- to this overlapping, during some seasons and in 

 some localities, there appears just before harvest what has In- some 

 been considered a supplementary second brood. 



In autumn the time of appearance of adults as between North and 

 South is reversed. In northern Michigan the adults of the fall brood 

 are abroad, under normal meteorological conditions, during the last 

 da3^s of August and first da^js of September. In Georgia and South 

 Carolina, under the same conditions, it may be the last of Novem- 

 ber or the first of December before they have all left the stub- 

 ble. Thus has the species adapted itself to the prolonged southern 

 summer, during which there is little or no food'for the larvte. "While 

 there are stragglers, the major part of the brood will appear and dis- 

 appear within the space of a few days, probably within a week, and 

 the flies. In- preference, will deposit their eggs on the younger plants, 

 those of one or two leaves seeming to suit them best. At this time 

 the .young larvae maketheir way downward nearly or quite to the roots 

 (fig. 10). The normal outcome of this brood is that the individuals 

 reach their development as larva?, pass into the flaxseed stage, and pass 

 the winter as such on the j^oung wheat plants. But here again the 

 earliest deposited eggs may produce adults before the winter sets in. 

 and the delayed individuals occurring at this time may unite and 

 another supplementary brood, as it has been termed, ma}" be produced. 

 The economic significance of this so-called brood depends much on the 

 weather, as, if winter sets in before the larvfe have sufficiently matured 

 to withstand its rigors, these must necessarily perish, while, if the 

 mild autumn weather is greatly prolonged, more or less of them maj' 

 winter over uninjured. 



LIFE HISTORY IX SPRING-WHEAT REGIONS OF THE NORTHWEST. 



The statements here made are based largely on the careful investi- 

 gations carried out by Mr. George I. Reeves, a special field agent of 

 this Bureau, during the season of 1905. This single season may have 

 been an exceptional one, in that the spring was ])ackward, the sununer 

 wet, and the mild autumn weather continued later than usual. The 

 results must not, therefore, be taken as wholly conclusive. 



In North Dakota the insect winters in the flaxseed stage in both 

 stubble and volunteer wheat, chiefly the former. V-'^^^g laying begins 

 late in May, and during seasons with phMity of rain the second brood 

 follows the first in quick succession, l)eing reenforced by the con- 

 tinued emergence of flies from stubble of the previous year. Here 

 the summer conditions are different from those in the East and South, 

 and the breeding season extends from about j\Iay 20 to October 1, or 

 throughout the entire summer. In other respects the habits of the 

 insect do not seem to differ from what thev are in the faU-wheat- 

 o-rowing section of the counti'v. 



