INDIRECT INJURIES CAUSED BY INSECTS. 135 



Russia ^ ; but this species with us is chiefly injurious to turnips 

 and garden vegetables. 



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

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

 deed the same, appears to be nearly related to the Musca pu- 

 milionis of Bierkander ^ ( Oscinis F.), accused 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 invariably destroyed, 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 stem 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 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 in- 

 jurious. It is also not unlikely that the new progeny, which 

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

 spring corn, which w^ould 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 apartments 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 created no small alarm 

 amongst agriculturists, lest it should prove to be the Hessian 

 Jly, so notorious for its depredations in North America ; but 

 Mr. Marsham, by tracing out the species, proved the alarm 

 to be unfounded.^ That there was suflScient cause for ajD- 

 prehension, should it have so turned out, what I have formerly 



' Kollar on Ins. injurious to Gardeners, &c. 94 — lOJ. 



2 Act. Stockh. 1778, 3. n. 11. and 4. n. 4. Marsham in Litin. Trans, ii. 79 



3 Linn. Trans, ii. 76—80. 



K 4 



