10 



the next; and, while the insect may prefer certain varieties over others, 

 this all comes to naught in years of serious ravages or where the sup- 

 posed distasteful variety is in a condition more satisfactory^ to the 

 insect at the time of oviposition. It is doubtful, however, if this can 

 be said of the attack of the second brood on the more matured plants, 

 as it is (juite noticeable that the ranker-growing- varieties with strong, 

 stiif straw are the least aU'ected. Then, too, among fall wheats in the 

 northern part of the country it is quite essential that a wheat plant 

 be able to send out tillers from the old roots of plants killed by the fly 

 (tig. 10), and that these tillers prove hard}^ enough to withstand the 

 winter. Therefore, in selecting varieties of wheat with a view to evad- 

 ing Hessian-fly attack, the farmer will do well to ignoi-e statements on 

 this point from those who have seed to sell and select from the varie- 

 ties known to do well in his locality such as are of strong, vigorous 

 growth, hardy, and with a stifl' straw. For some reason the durum or 

 macaroni wlwats do not seem to attract th(^ fly, at least not the second 

 brood. In going over flelds of this kind of wheat in sections where 

 other spring wheats were suflering from attack by this pest, it was 

 rarely found on a stem of niacaroni wheat, while any straws of other 

 varieties growing from seed that had become intermixed were almost 

 invariably infested. Whether this will hold good in case of the young 

 plants it is as 3'et impossible to say, because of the difficulty of telling- 

 to what varieties the young plants belong. Infested plants have been 

 found in flelds of 3'oung macaroni wheat in some considerable numbers; 

 but these plants ma}' have been of other varieties, as the flelds had been 

 used for other varieties the year before, and besides the seed itself may 

 have been impure. 



3IETEOROLO(iICAL EFFECTS. 



All who have carefullj" studied the Hessian fly, under various field 

 conditions during a series of years, have noted that weather conditions 

 have an important influence on the insect. Especially is this true in 

 its economic relations to the grains it attacks; hence, in the applica- 

 tion of preventive measures, these weather conditions become of vital 

 importance. 



Man}" farmers place much stress on the effect of cold weather or 

 even of frosts in terminating the flies' work in the fall, and it is for 

 this reason that many tr}^ to delay wheat sowing until after there has 

 been a sharp frost. The facts are that the females will be abroad and 

 ovipositing in freezing weather, and Mr. W. J. Phillips has found 

 by experimentation that the eggs will remain in a temperature of 86^ 

 F. for seventy-two hours with no other efl'ect than to delay their 

 hatching that much longer. This is about the temperature at which 



