296 DESTRUCTIVE INSECTS. 



of these galls and the pulpy consistence of their sub- 

 stance, in which the astringent quality and colouring 

 property of the tree are notably concentrated, are 

 interesting circumstances ; showing that the uncon- 

 scious nymph not only obstructs the direct current of 

 the sap, but seems from its operations on the interior 

 of the cavity to give form and consistence to the 

 exterior, altogether different from the other expansive 

 processes of the plant. From this incidental pro- 

 duction, the physiologist may remark the wonderful 

 versatility of the cellular body when disposed as 

 parenchyma, and of its other structure in the shape 

 of hybernacula when affected by the insertion of an 

 egg of the Cynips quercus-gemmce. This insect, it 

 appears, has the power of introducing its ovipositor 

 into the very centre of the bud; there the egg 

 obstructs the elongation of the axis, throwing all the 

 growth into the hybernacula and incipient leaves, 

 both of which become unnaturally incrassated, and 

 form a monstrous imbricated bud round the larva 

 while it undergoes the different changes of its youth. 

 The small tubercles on the leaves of the Glechbma 

 are caused by a species of these insects. 



Haltiaca oleracea. The turnip-fly or beetle is a 

 most injurious insect, as well in gardens as in fields. 

 Every species and variety of the Brassica family are 

 preyed on by this fly, and in some seasons occasion 

 great loss of time and labour to the farmer. They 

 first appear in gardens, early in the spring, on radish, 

 cabbage,- cauliflower, &c, feeding chiefly on the semi- 



