210 



THAT S IT ; 



before' the insect has escaped, and are of great 

 importance as a source of black dye, and also as 

 a material in the manufacture of writing ink. 

 The white galls are those from which the insect 

 has departed; they answer the same purpose 

 in an inferior degree. 



Gall insects are remarkable for 

 the wonderful mechanism which 

 enables them to puncture the 

 different parts of plants. To the 

 operations of these insects we 

 owe the production of oak-apples, 

 or nut-galls, the reddish-brown 

 hair, which forms the gall of the 

 rose; the artichoke galls, found in 

 oak-buds ; the leafy galls, found 

 upon dyer's broom; the rose-like 

 clusters, found upon the rose- 

 willow ; the woolly balls on haw- 

 thorns and willows, and the cur- 

 rant-galls, on the catkins of the 

 oak. The machinery employed 

 is always the same, though the 

 species of gall-insect varies in 

 each example. This machinery 

 consists of what may be com- 

 pared to a needle contained in a 

 sheath, and having remarkable 

 powers of extension derived from 

 the peculiar construction of the 

 body of the insect ; so much so, 

 that the needle can be extended 

 to twice the length of the insect 

 itself, within which it is lodged 

 in a bent form, following the 

 curve of the body, and running 

 along the back, making a turn at 

 the breast, and then assuming 

 the curve of the belly, and ap- 

 pearing again near the point 

 whence it had originated.* 



Among the insects that live 

 upon the leaves of the oak, is 

 that interesting species, the leaf 

 roller, 4. The caterpillar, 5, of 

 this moth rolls up leaves in a 

 very ingenious manner, so as to 



* Tomlinaou'b Cyclopedia of Arts and Manufac- 



form a convenient retreat, 6, in 

 which it ordinarily resides, the 

 centre of the roll being open. 

 The roll is secured by various 

 little bundles of silk, 7, attached 

 to the leaf. The moth, 8, flies 

 away from this habitation. 



4 



583. 



A close examination of the 

 oak will show that it is more 

 resorted to by i?isects than almost 

 any other tree. Some of these 

 live upon the solid wood ; others 

 upon the wood in a state of decay. 

 Various species reside beneath the 

 bark ; a great number feed upon 

 the leaves ; while others infest 

 only the stems and buds. 



The acorns, as well as being 

 useful for the food of swine, and 

 other animals, are devoured by 

 the larvae of some insects. 



The purple emperor butterfly 

 makes the leaves of the oak a 

 favourite resting place, but does 

 not feed upon the tree. Various 

 species of aphides also infest the 

 oak, and lace-winged flies, by 

 which the former are pursued. 

 And upon various parts of the 

 tree clusters of insect eggs are 

 commonly to be found. 



The mistletoe is the only truly 

 parasitic plant which grows on 



