No. 6. DEPARTMENT OF AGRICULTURE. 475 



a fourth generation of adults developed from this third one, by 

 August 5, and from these the fifth generation appeared September 

 4, and sixth by October 18, which deposited eggs that produced 

 larvae which changed into the puparia and went into winter quar- 

 ters. 



WHEAT IS GOOD FOOD 



These experiments were made in France where usually climatic 

 conditions are most favorable for the development of the Hessian 

 fly. The likelihood is that it is seldom the case that anything like 

 such conditions prevail in any section of this country, that food 

 for the larvae such as growing wheat, rye and barley, which seem 

 to be the only food plants upon which the larvae feeds, are provided in 

 nature in anything like sufficient quantity to develop such a num- 

 ber of broods, but in some instances similar conditions may have 

 prevailed last season. During July, August, September, October, 

 and even into November of 1910 this dry and cool weather pre- 

 vailed. 



BRED WITH EASE 



In many places on the farm, either in the unplowed stubble field, 

 for many farmers on account of the drought did not plow until late, 

 or in the stubble field sown Avith grass there was sufficient moisture 

 for the fly to pass with ease through all its stages of development 

 and with few of its parasitic enemies present as was the case last 

 year, and with sufficient volunteer wheat growing either on the un- 

 plowed stubble field or on the field sown with grass to furnish food 

 for the larvae, ideal breeding places were provided on the farms 

 of well nigh all wheat raising farmers, for the development of per- 

 haps three or four broods of tin's post during the past season. 



LIKE STUBBLE FIELDS 



The stubble fields sown with grass is an especially favorable 

 place for the breeding development of the Hessian fly, because if 

 there has been a fair stand of clover and timothy it furnishe<s pro- 

 tection from the dessicating heat of the sun. If this has not been 

 the case weeds will soon spring up to do the same thing. Volunteer 

 wheat comes up early and late, depending on location, and grows 

 and furnishes food for the larvae which go on their way of repro- 

 duction unmolested by inspectors or poisonous sprays. 



FREQUENT CULTIVATION 



The stubble field that is to be plowed to be sown with a second 

 crop of wheat may have similar conditions to the ones already 

 described as pertaining to the field sown with grass, but in this case 

 if thhe field is plowed early and after plowing frequentlj^ cultivated 

 to prevent volunteer wheat from growing, no food for the larvae is 

 provided, and consequently no adult flies can develop. This is 

 farming to destroy the Hessian fly, whereas sowing grass with the 

 wheat and raising weeds after harvest as is the case in the stubble 

 field sown with grass, is farming to raise Hessian flies, because here 

 the most favorable conditions prevail. 



