1899] HESSIAN FLY. 39 



published by the United States Department of Agriculture (referred to 

 ante), attention is strongly drawn at p. 42 to the great importance of 

 destroying the pupario , or chrysalis-cases, of an infested crop by burning 

 the stubbles, or by destroying the chaff in which these "flax-seeds"- 

 are to be found after threshing. 



From circumstances of climate, custom, and also from straw being 

 in this country cut so low that much of the infestation is carried off 

 the field with it, the plan of burning the stubbles is not so applicable 

 with us as in the United States. Something, however, might be done 

 in case of straw being noticed to be badly infested towards preventing 

 flax-seeds left in the short stubble developing to fly, by " skimming," 

 and then dragging the rubbish together and burning it. 



Burning the chaff and infested light screenings is a very imjwrtant 

 point. The light screenings, which are chiefly of dust, small weed 

 seeds, and the like, being thrown down together by the threshing- 

 machines, there is little difficulty or expense in gathering them up and 

 destroying them. If it is troublesome to burn this infested material, 

 it may be thoroughly mixed in wet manure. This would not certainly 

 destroy the weed seeds, but it would make an end of the puparia. 



Objections have been raised (theoretically) to this treatment, that 

 thus we destroy the parasites which might be in the Hessian Fly 

 puparia, or chrysalis-cases, and which anight develop into little parasite 

 flies, and might fly to the Wheat and Barley fields, and there destroy 

 the Hessian Fly in its embryo state. But this benefit is problematical, 

 and if we burn the light screenings and the contents, we kill the 

 Hessian Fly in its young state thoroughly and undoubtedly, whilst our 

 hand is on it, without waiting for the involved considerations of letting 

 it go to do certain harm, and the parasites to do an uncertain amount 

 of good. 



At one time the matter of preservation of infested screenings was 

 so strongly endeavoured to be upheld here in some quarters (though 

 never, so far as I am aware, by those with good practical knowledge 

 of the bearing of the subject), that the late Prof. Eiley, Entomologist 

 of the U.S.A. Dept. of Agriculture, wrote me especially on the subject, 

 saying that he had no doubt that, whatever might be the case in 

 America, in this country the right course ivas to destroy the puparia. 



Now, in the work of Prof. Osborn, wliich is an admirable digest of 

 information up to date, we have the recommendation (as one of the 

 standard remedies most generally applicable) to destroy the puparia 

 when and where we can by burning tlie stubble, or burning chaff and 

 infested screenings ; and personally I would most earnestly advise 

 all concerned in this country not to listen to any unproved theories 

 on the subject, but just to destroy the pest when it is in their 

 power. 



