Warr.—Leaf-mining Insects of New Zealand. 329 
proceeding downwards between the midrib and the outer margin of the 
leaf; it never crosses the former barrier. As the mine descends, the angles 
of the zigzag increase in size. All mining is carried’ on in the bulb of the 
larva having mined from one into the other, and perhaps later back 
again. One may find-not a mine, but only a very faint and slight impression 
of one, on the surface of an otherwise sound leaf; this is due to the pressure 
caused by the larva mining in the leaf next against it while in the bulb. 
Never more than one larva will be found to be mining in one half of a 
leaf, but both halves of the same leaf may be mined by separate larvae. 
In such cases there is, as one would expect, a direct parallelism in the 
course of the mines. Occasionally very short blind branches or ends may 
be found at the angles of the mine, the midrib or outer edge of the leaf, 
In the next to last larval stadium the larva, practically mature, ceases 
w some mm. wide), and, leaving the gallery, 
forces its way, no longer downwards, but straight up for about 14-2 in., 
till just below where the two contiguous leaves begin to separate ; here, 
lying with the head uppermost and parallel to the axis of the leaf, it 
rests awhile; its body becomes much distended with clear fluid, and 
within it can be seen the next stadium larva about two-thirds the length 
of the old distended skin. When ready it bites a hole in the side of the 
old skin and emerges from it, the cast skin being flattened against the 
surface of the leaf, to which it may adhere for many months. The larva 
is now in its final stadium, the whole of which is occupied in the prepara- 
tion of the cocoon, and lasts eight to fourteen days. Total length of 
the mine, possibly 3—4 ft. ° 
