LEAF MINERS. 



175 



cylinder, they make their way between the two membranes, and 

 there remain until they have undergone their transformation. 



The reader must often have seen the leaves of garden plants 

 and trees, especially those of the rose, traversed by pale wind- 

 ing marks, that look something like the rivers upon a map, and 

 having mostly a narrow dark line running exactly along the 

 middle. These curious marks are the tracks which are made 

 by the various leaf-mining insects, while eating their way 



LEAF MINERS AND ROLLERS. 



through the leaf in which they pass their larval state. In most 

 cases, when the insect has completed its term of larval existence, 

 one end of the track is found to be greatly widened, and to 

 contain either the pupa itself or its empty case. 



The track differs considerably in shape, according to the 

 insect which makes it. Sometimes it winds about in the middle 

 of the leaf, crossing itself more than once in its progress. 

 Sometimes it proceeds in a nearly straight line across the leaf, 

 and very frequently, especially in deeply-cut leaves, it follows 



