42 THE SCIENCE AND PEACTICE 



CHAPTER VIII. 



ON THE INJURIES CAUSED BY INSECTS. 



Root-crops are especially liable to injury from the 

 depredations of insects. Thus the turnip may have its 

 seed more or less destroyed by weevils. Immediately 

 the seed appears above the ground, commences the 

 attack by the turnip flea-beetles. The bulb is pierced 

 by beetles, ending in those excrescences called " tur- 

 nip-warbles ;" and there is reason to think that even 

 the root-fibrils are in some soils made the depositories 

 of the eggs of insects, which give rise to extraordinary 

 malformations. 



Carrots and parsnips are liable to have the best- 

 grown root made useless by its being pierced and 

 eaten by the larvaB or grubs of a small fly, knoAvn as 

 the Psila rosce. 



Even the mangel-wurzel, which has been so 

 strenuously recommended as a substitute for the 

 turnip on account of its freedom from insect attacks, 

 and connected with which Curtis only describes a 

 single insect, a leaf-miner, called Anthomyla Beta;, 

 upon which he remarks that " these insects will 

 seldom cause any loss to the mangel-wurzel crops 

 should they ever abound to any extent." In spite, 

 however, of this, we find that the increased growth 

 of this crop has caused a corresponding increase in 

 the insect, to such an extent that, during the last two 

 seasons, many crops have entirely failed from its 



