40 Agricultural Experiment Station, Ithaca, N. Y. 



.immediately begins to feed upon the outer layer of cells or epidermis 

 of the leaf, usually upon the under side . A few hours later the larva 

 makes for itself a tube, open at both ends, of silk in which pellets of 

 excrement are intermingled. This tube is usually made alongside the 

 mid-rib of the leaf, but sometimes near a large vein. These tubes are 

 the homes of the larvae from which they sally forth to feed upon the 

 surrounding tissues and into which they retreat when disturbed. The 

 larvre further protect themselves by spinning, as they go, a thin layer 

 of silk, in which the natural pubescence of the leaf is mixed, over 

 their feeding grounds. This silken web extends over the tube also, and 

 being gradually thickened as the larva grows, the tube is scarcely visi- 

 ble from without. As the larva increases in size and the area over 

 which it feeds becomes larger, the tube is enlarged and lengthened 

 along the mid-rib, sometimes becoming nearly one inch in length. The 

 silken web under which the larva feeds covers the entire field of opera- 

 tions but is so thin near the edges where the larva has last fed as to be 

 scarcely visible. The excrement of the larva being retained by the 

 web appears as little black pellets scattered here and there over the 

 feeding ground. 



The larvae feed almost entirely upon one epidermis and the inner 

 tissues of the leaf, leaving the net-work of little veinlets and rarely 



Fig. 7. — Leaf showing the work of a young larva during the summer. Natural size. 



eating through the opposite epidermis which thus forms the floor of its 

 feeding grounds. The veinlets and epidermis remaining soon turn 

 brown and die; and as the epidermis is quite transparent the work of 

 the larva is rendered conspicuous from either side of the leaf. Rarely 

 more than one larva works on a leaf. Sometimes two leaves are 

 fastened by the silk of the web, and the larva then works between the 

 leaves, feeding mostly on the tissues of one . 



The larvae continue to feed in this manner during July and August, 

 and some may be found feeding in September. The area over which a 

 larva has fed is very irregular in outline and usually covers less than 

 one-fifth the area of the leaf. It usually extends along both sides of 



