38 



On the Wheat-midfjc. 



which I had obtained specimens had been attacked bj the midge : 

 indeed some larva? were present in ahnost every ear, and many 

 of them were encased in the manner ah'eady alluded to. I was 

 particularly struck with their abundance in some ears of a tall 

 description of revets. In one well-grown ear I found only nine 

 sound grains, all the rest having been reduced to an abortive state 

 l)y the insect. The farmer to whom the wheat belonged assured 

 me that he was never so much disappointed in a crop before. It 

 appeared to thrive well, and looked fine, but the yield was at 

 least one-third less than he had expected it would have been. 

 Part of the deficiency might have been owing to the rust or red- 

 rug with which the chaft" and leaves had been attacked ; but from 

 Vrhat I saw of the effects produced by the midge, I was satisfied 

 that the mischief was chiefly owing to this insect. I next ascer- 

 tained that numbers of the larvae might be found on the floor of 

 the barn where the wheat was threshed ; and next, when the wheat 

 was dressed, I found that some of the larva? fell through the wire- 

 gauze together with the dross, but that the greatest number were 

 blown out with the chaff. Upon sifting the chaff through the 

 sieve usually employed to clean it for the cattle, all the larva* which 

 have been blown from the machine pass through with the dust. 

 In order to form something like a definite notion of the numbers 

 of the larvae which are housed with the wheat, T endeavoured to 

 ascertain the number which might be picked from a certain 

 measure of this chaff-dust, and thence to calculate the numbers 

 contained in a bushel of it. Those larvae which were encased 

 and appeared full grown, and ready to turn to pupae, I numbered 

 apart from those which were imperfect, and many of which were 

 dead. The following table will show the result of this inquiry ; 

 and I shall make a few remarks upon the inferences we may 

 deduce from it: — 



