VOL. III. ] Leaf-Miner. 235 
Leaves containing larve were collected on May 4 of the same 
year, and put ina jar with earth to breed, but the larve all seem- 
ingly shriveled up and became hard and dried. At this date more 
than two-thirds of the larve had left the leaves. 
The spring of the present year the leaves of the cottonwood had 
been out not more than one week when it was found, April 21, 
1892, that they contained good-sized larve of this miner. It would 
therefore seem that the eggs must be deposited in the leaf-buds be- 
fore the leaves appear, perhaps about the time the buds begin to 
swell. 
_ On April 25 of this year, most of the larva were apparently full- - 
- grown, and accordingly a good number of small branches bearing 
leaves filled with healthy larve were put in a breeding cage, the 
branches being inserted in a receptacle which was kept filled with 
water. The leaves remained green and healthy for days, until all 
the larve had disappeared. The next day, April 26, a large num- 
ber of the larve had already left the leaves, and were crawling on 
the earth in the bottom of the cage. They seemed to manifest a 
migratory instinct, and did not appear inclined to bury themselves 
at once inthe soil. The migratory larva seems to lose the blackish 
dots on the anterior segments both above and below, and is entirely 
of a whitish color and somewhat shorter than before. Two orthree 
of them were noticed going into the earth, but they were subse- 
quently found perfectly hard and dried, and this was likewise the 
fate of all the others, which shriveled up and died on top of the earth 
within a day or two. They would not crawl under chips which 
were placed within the cage. All natural conditions had been care- 
fully studied and provided, but to no avail. On April 29, the larve 
had all left the leaves in the breeding cage. Some very small larvae 
ones. 
- Five of these miners were often found in one leaf this season, but 
the leaves of the trees were not so totally destroyed as in 1891. In. 
one case even seven larve were found in the same leaf. They all 
begin separately, and work till their mines meet. The two skins 
of the leaves then become filled with the very fine black frass or ex- 
_crement of the larve. They feed by day, and so far as observed ~ 
always with the venter toward the upper surface of the leaf. They 
leave the leaf by making an incision in the upper skin just in the 
were at work on April 25, along with the apparently full-grown 
