168 INDIRECT INJURIES CAUSED BY INSECTS. 



Mr. Markwick has given us the history of a fly that at- 

 tacks wheat in a later period of its growth, which, if it be not 

 indeed the same, appears to be nearly related to the Musca 

 Pumilionis of Bierkander a , accused by him of being ex- 

 tremely injurious to rye in the spring. Our insect was 

 discovered on the first sown wheats early in that season, 

 making its lodgement in the very heart of the principal 

 stem just above the root, which stem it invariably destroy- 

 ed, giving the crop at first a most unpromising appear- 

 ance, so that there seemed scarcely a hope of any produce. 

 But it proved in this and other instances that year (1791 ) 

 that the plant, instead of being injured, derived great be- 

 nefit from this circumstance ; for, the main stem perish- 

 ing, the root (which was not hurt) threw out fresh shoots 

 on every side, so as to yield a more abundant crop than 

 in other fields where the insect had not been busy. These 

 flies therefore seem to belong to our insect benefactors; 

 and I should not have introduced them here, had it not 

 been probable that in some instances later in the spring 

 they may attack the lateral shoots of the wheat, and so be 

 injurious. It is also not unlikely that the new progeny, 

 which is disclosed in May, may oviposit in barley or some 

 other spring corn, which would bring the next generation 

 out in time for the wheat sown in the autumn. — These 

 flies are amongst the last, and, in some seasons, the most 

 numerous, that take shelter in the windows of our apart- 

 ments when the first frosts indicate the approach of winter, 

 previous to their becoming torpid during that season. 

 When this little animal was first observed in England, it 



1 Act. Slockh. 1778. 3. n. 11. and 4. n. 4. Marsham in Linn. Tram. 

 ii. 70. This insect probably belongs to Latreille's genus Mosillus, and 

 seems related to Mpsi/lus arouatut, Gen. Crust. # Ins. iv. 357. 



