LIFE-HISTORIES OF SAWFLIES. 965 
the birch,—and in the second place by a discovery of Mr. C. 
Ritsema, who found the perfect insect, in the month of May, at 
Ginneken, sitting on a small birch tree. Mr. Ritsema captured 
the insect, which was a female. 
The Scotch entomologist above named communicated to 
me the followimg particulars respecting the life-history of this 
insect :— 
The egg is always laid at the tip or on the edge of a birch 
leaf, never in the middle of the leaf, and, as a rule, only one egg 
is laid on a leaf; sometimes two eggs may be found, and even, 
once in a way, three. On emerging from the egg the larva 
begins forming a broad mine in the leaf, and the upper surface 
above the mine immediately becomes black or dark brown. The 
space between the surfaces of the leaf is regularly enlarged, so 
that, by the time the larva has attained its full size, about 
three-fourths of the whole upper surface has been undermined. 
The little animal is very careful always.to keep its habitation 
clean, and for this purpose makes an opening at the edge of the 
leaf, through which its excreta are ejected. In the mine the 
larva lies on its back, feeds in this position, and rests after 
feeding at the spot where it has last mined. When full grown 
the larva spins within the leaf a thin brown cocoon of a circular 
shape and semitransparent; this cocoon is so roomy that the 
larva can easily move itself in all directions. 
There are two broods in the year; the first occurs in June, 
July, and August; the second from the end of August through 
September and the rest of the year into the following spring, 
when the larva changes to a pupa. The spring pupa then 
remains a fortnight or three weeks in the cocoon before the 
imago makes its appearance. 
The young larva (August) is dull brownish yellow, and has a 
broad green longitudinal line on the back after the fourth 
segment. At this stage the head is brown at the sides, yellow 
in the middle, and has projecting Lrown jaws. On the middle of 
the first segment of the body are two brown triangular spots, and 
on each of the following two segments are two fine transverse 
lines. At the sides the segments project strongly in the middle. 
(See fig. 2). 
The full-grown larva is deep or pale yellow (the individuals 
differ in colour); the first three segments, which form the 
2M 
