Wheat Flies. 293 



Upon the same insect, in the volume of the Linncean Transactions 

 above referred to, in which he conjectures that, as the fly is bred 

 so early as May, and the early-sown wheat does not spring up 

 until some time after the end of September, there must be an 

 intermediate brood of these flies * ; and, with a view to ascertain 

 this point, he offered the following hints for observation : — 

 " When it appears evident that a fly has attacked a field of wheat, 

 rye, &c., watch carefully the animal through all its stages, but 

 more especially when the fly takes wing; observing on what plant 

 it settles, and whether it is partial to any particular plant; and, 

 if this can be determined with precision, attend to see it deposit 

 its eggs, carefully examining whether it lays more than one at a 

 time. If, afterwards, the larvee appear on those plants, observe 

 in what manner they feed ; continuing the remarks till the perfect 

 insect appears ; when it must again be watched with attention, and 

 traced to its next place of depositing its eggs, to determine whether 

 wheat or rye be its natural food in spring, or whether these plants 

 be only in particular seasons, when its own natural food may have 

 failed ; for Mr. Markwick takes notice that it was only the early- 

 sown wheat that was affected." He likewise suggests, that, as it 

 appears from Mr. Markwick's experiments, that the wheat throws 

 out lateral shoots, it is not advisable to adopt Bjercander's 

 advice of picking out and burning the stems; but that pinching 

 the centre leaves just above the crown of the root, where the 

 insect is usually found, may, perhaps, effectually destroy it, and 

 leave the plant in a state to throw out its side shoots. 



Fallen, the celebrated entomologist of Sweden, in his work 

 upon the Diptera of that country, has described the Musca pu- 

 milionis, under the genus O'scinis, as being of common occurrence 

 in the months of June and July, with the observation: — " The 

 larva of this fly resides within the stems of wheat, which it destroys, 

 and is described by Bjercander. The description of the perfect 

 insect, however, agrees equally v^^ell with O. lineata Fabricins, 

 and O. pumilionis ; no description being given of the position of 

 the nerves of the wings. It is, indeed, most probable, that the 

 larvae of both species inhabit the same situations. The length of 

 one line, which Bjercander attributes to the latter species, agrees 

 with the insect here described ; which I therefore consider as 

 identical with O. pumilionis. A specimen, however, reared from 

 a larva found in a stem of wheat, transmitted by Bjercander 

 himself to Professor Lidbeck, is entirely black, and belongs not 

 to this species, but is O'scinis frit of Linnaeus; whence it is 



* Mr. Marsham observes that they are not uncommon, as he frequently' 

 found them, in autumn, on umbelliferous plants. It is much more common to 

 observe them in great numbers in our apartments; during the autumn of 

 1834, they literally swarmed in the houses in the immediate neighbourhood of 

 the metropolis. The white ceilings of rooms appeared quite discoloured by 

 their numbers. 



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