50 BULLETIN 322 



the leaves (Fig. 7). The great majority of the eggs, in the vicinity 

 of Ithaca, are deposited during the first part of June. In 1910 an 

 abundance of eggs was found in the field on June 10. The time will 

 vary somewhat, however, in different years. 



The summer habits of the larva 



When the larva hatches from the egg it bores directly through the floor, 

 or bottom side, of the eggshell, and thence through the epidermis of the 

 leaf into the inside. Mr. Fink demonstrated this habit of the larva very 

 clearly, for he found specimens in the act of entering the leaf in this manner. 

 Mr. Fink and the writer were puzzled by not finding any openings in the 

 leaves_ through which the larvae had entered, until they found individuals 

 entering directly from the egg. The larva, being exceedingly small, 

 mines very slowly at first; but after a few weeks the light-colored mine, 

 with the dark body of the miner showing through, is seen. The light- 

 colored eggshell clings to the leaf for many days, but if it is tipped over 

 one may find the opening through the epidermis to the mine. 



The larvae live within the leaves of the larch, gradually enlarging their 

 mines until September. The leaves as they are mined appear russet ed. 

 As the tiny miner grows and enlarges its burrow, it packs the empty part 

 of the mine with excrement. During 1910 the miners began to emerge 

 from their burrows in the larch leaves and to make their winter cases 

 during the first half of September. Sometimes these cases were made of 

 the old leaves in which the larvae had lived all summer, but often they 

 were made of newly mined leaves. When the larva gets ready to form 

 its winter case it cuts off the end of the leaf in which it has lived all summer. 

 The larva then cleans out the burrow, goes to the lower end of the mine 

 next to the base of the leaf, and cuts off enough of the mined leaf to make 

 its case. The mine of the larva is large enough to allow its occupant to 

 turn around with ease and whenever occasion demands. The larva is 

 very neat in its habits, for it backs up from time to time in its work, pro- 

 trudes the posterior end of the body, and ejects the excrement outside. 

 Occasionally one finds a case still bearing the eggshell of an egg laid nearly 

 three months previously. The inside of the case is lined with a very thin, 

 delicate layer of silk. 



Some of the larvae, as already noted, make cases out of new leaves. 

 After the middle of September one often finds naked larvae wandering 

 over the leaves of the larch. These are the ones that have left their old 

 mines and have gone in search of new leaves to excavate for their winter 

 cases. When a suitable leaf is found the larva mines it out and makes 

 the case in the same way as described above. 



