80 LEAF-MINING INSECTS 



a leaf miner only during its early larval life. Its later sur- 

 face-feeding habits have been well described by Comstock 

 (1925) as follows: 



The leaves of an infested tree present a strange appearance. 

 They are perforated with numerous elliptical holes and marked by 

 many more or less perfect ring-like patches in which the green 

 matter of the leaf has been destroyed, but each of which incloses 

 an uninjured spot. These injuries are produced as follows. The 

 young larva cuts an oval piece from a leaf, places it over its back 

 and fastens it down with silk around its edges. This serves as a 

 house beneath which it lives. As it grows this house becomes too 

 small for it. It then cuts out a larger piece which it fastens to the 

 outer edges of the smaller one, the larva being between the two. 

 Then it fastens one edge of the case to the leaf by a silken hinge 

 so that it will not fall to the ground "cradle and all" and then 

 turns the case over so that the larger piece is over its back. When 

 it wishes to change its location it thrusts out its head and fore- 

 legs from the case and walks off looking like a tiny turtle. When 

 it wishes to feed it fastens the case to the leaf and, thrusting its 

 head out, eats the fleshy part of the leaf as far as it can reach. 

 This explains the circular form of the patches, the round spot in 

 the middle indicating the position of the case. 



Professor Herrick has described its leaf mining and other 

 habits in the paper (1923) from which we have already 

 quoted (p. 48) concerning its egg-laying. W r e quote now 

 further : 



As soon as the egg hatches, the young larva begins at once to 

 mine in the tissues of the leaf, and it continues to live as a miner for 

 probably about ten days. 



In general, the mine is irregularly linear, although it tends to 

 enlarge somewhat toward the terminus and to become a blotch. 

 The mines are most conspicuous from the upper surface of the 

 leaf, and may be very numerous. 



The young larva is greenish brown in color, with a dark brown 

 head. The body is somewhat flattened, the prothorax is broad- 



