148 LEAF-MINING INSECTS 



July and are most often to be found among the hairs on the 

 under side, particularly along the midrib. 



After two weeks (i.e., towards the end of July) the eggs 

 hatch. The larvae do not enter the leaves directly through 

 the egg shells but come out on the side of the eggs and move 

 about on the surface of the leaves for several hours before 

 obtaining an entrance. They live as miners within the 

 leaves for about fourteen days making elliptical brown mines 

 and ejecting from them black powdery excrement. About 

 the first week of August in the northeastern United States 

 they form their first cases, cutting elliptical pieces from the 

 upper and lower walls of the mine and sewing them together. 

 Moving off the leaves in mid September they seal the mouths 

 of these sheaths firmly to the branches and remain until 

 spring as minute half-grown caterpillars. 



As soon as the buds begin to swell in the spring the larvae 

 move out upon them and bore into the succulent expanding 

 tissues. Later when these are partially unfolded they 

 attack the young leaves, the stems of flower or fruit, or the 

 downy growing twigs. They feed and grow rapidly, and 

 they prolong one side of the elliptical case into a tube of 

 fragments of tissue and silk. By the time this tube equals 

 or exceeds the original length of the elliptical case the leaves 

 are fully expanded and their cuticles fairly resistant. The 

 larvae then begin to mine from the cases and from one of 

 the earliest mines make a new case. 



They attach the cases to the leaf and begin to mine in the 

 usual way but instead of making a small rounded or poly- 

 gonal mine with the feeding puncture near the center, they 

 make a larger one and get away from the case entirety. The 

 new cases which they cut from the upper and lower cuticles 

 of these mines are in shape very unlike their first ones. At 

 first they are elongate and flattened but as the larvae move 

 about in them and line them with silk they become more 



