INDIRECT INJURIES CAUSED BY INSECTS. 169 



Mr. Mark wick has given us the history of a fly that 

 attacks 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 , (Oscinis F.) ac- 

 cused by him of being extremely 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 invariablydestroyed, giving the crop at first a most 

 unpromising appearance, 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 benefit from this circumstance ; 

 for, the main stein perishing, 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 in- 

 sect 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 



the mischief to the wheat, while those of the Zabrus contributed 

 rather to lessen their numbers than to destroy the corn." But this 

 query does not account for their being found, when in the perfect 

 state, attacking the ear. I have seen cognate beetles devouring the 

 seeds of umbelliferous plants. 



a Act. Stockh. 1778. 3. n. 11. and 4. n. 4. Marsliam in Linn. Trans. 

 ii. 70. 



