io6 Oh/ervations on the HeJ/ian Fly. 



but if the ftubble of wheat were to be univerfally burnt, turned 

 over with the plough, or dellroyed in any other manner, foon 

 after harveft, and this- were to be done for feveral years toge- 

 ther, I have Htde doubt but that it would prove an effeftual 

 mean of deflroying the whole fpecies : I here mention only the 

 flubble of wheat, becaufe it is not very probable that the fpecies 

 would be continued long on rye, more efpecially as that can be 

 fown much later than wheat, without injury from the winter ; 

 but the ftubble of rye might, if neceflary, be as eafily deftroyed 

 as that of wheat ; and if in aid of this the belt fort of bearded 

 wheat were to be ufed, and that to be fown as late as poflible 

 confiftent with a good crop, it would be ftill more likely to 

 fucceed. With refpeft to the probability of their being 

 imported from any foreign country, I fhall make only one 

 remark, that from the foregoing account it appears evident, 

 that they may be removed from their natural htuation in the 

 field, and be kept alive long enough to be carried acrofs the 

 Adantic ; from which circumftance it appears poflible that 

 they might have been imported in ftraw or ftubble. It has 

 been generally remarked that in fpreading over the country 

 they go between twenty and thirty miles in a year ; but as they 

 are a fly twice in the fame feafon, it appears probable, that the 

 fly itfelf never goes much fardier than twelve or fifteen miles. 

 Before this fubjeft is concluded, it ought to be remarked, that 

 the truth of what has been here faid concerning the nature of 

 this infeft, and the feveral generations through which is pafl^es 



