SPINNERS AND WEAVERS 5 



flat portions of the leaf. By pressing upon these 

 threads with the weight of its small body, the 

 caterpillar gives a further turn to the coil, and 

 prevents its springing back by attaching a short 

 new thread at an angle between the old thread 

 and the leaf. Other threads are attached farther 

 up the coil and farther out on the leaf, and these 

 are shortened and tightened in a similar manner, 

 until the little Green Tortrix larva has rolled up 

 sufficient of the leaf for its purpose. 



If the young leaf has so far hardened that the 

 midrib has too much spring in it, the caterpillar 

 overcomes this tendency by reducing its thickness 

 and its resistance with its jaws. In this tube the 

 caterpillar lives, feeding upon the inner folds of its 

 house, and when it has attained to its full develop- 

 ment, as a larva, spins a slight cocoon and changes 

 into the chrysalis condition, from which a little 

 later it emerges as the beautiful little moth with 

 pale green wings known as the Oak Tortrix (Tortrix 

 viridana). This is the insect that in some years 

 almost entirely defoliates our oaks before mid- 

 summer, though apparently without inflicting any 

 serious damage to the tree, which is soon well 

 clothed again. 



Similar rolled leaves may be found upon many 

 trees, the work of other species of Tortrix, which 

 pursue their industry upon similar lines by the 

 use of the simple silken thread. In some cases, 

 however, the same end is attained in a more 

 simple manner the edges of the leaf being spun 



