Mar. 25,1914 
Cambium Miner in River Birch 
473 
on June 19, 1913, was 30 mm. in length and 1 mm. in diameter. The 
hooklet is shiny black and chitinized, the exposed portion being more 
highly chitinized than the rest. The hooklet complete (cephalopharyn- 
geal skeleton) dissected out is shown in Plate LXI, figure 1, a. Back of 
the large hooklet are two smaller toothlike processes, one on each side, 
the position of these being shown at b. The anterior spiracles at c and 
the posterior pair at d are a very pale yellow, and their position is shown 
in outline. At the caudal end of the larva are two padlike surfaces, very 
faintly raised from the surface of the body, reaching nearly around the 
circumference of the body and covered with numerous brown, hooklike 
hairs or bristles. Several stages of the larvae were observed, and the 
only noticeable difference was in their size. 
If theJarva reaches the base of the tree before the time to pupate, it 
will turn and mine up the cambium for some distance; on one occasion 
the larva retreated for 6 feet, then returned, thus encircling the root, and 
followed it for 2 feet from the trunk. The exit hole is sometimes made on 
the side of the root, but generally it is on the underside, and the larva 
pupates immediately on emergence. The pupae were found from one- 
half to one inch from the exit hole. A portion of river birch (Beiula 
nigra) with the bark removed is shown in Plate LX, figure 1, to illustrate 
the larval mines, while figure 2 is part of a cross section showing the 
“pith-ray flecks” from above. 
The only larva that was reared by the writer, and in fact the only one 
that reached maturity, was placed in a large vial July 30, 1912, with a 
piece of freshly cut river-birch bark, the inner surface of which was 
covered freely with fresh sap. A piece of gauze was placed over the 
opening of the vial. On August 6, 1912, at 8.30 a. m., the larva com¬ 
menced pupation, first becoming rigid and then changing to deep yellow 
at both ends, while the central portion remained the natural white color. 
It was 25 mm. in length and 1 mm. in diameter, but by noon it had 
decreased to about 10 mm. in length and increased to 2 mm. in diameter. 
Both ends had changed to dark brown and were perfectly formed, as in 
the pupa, and the middle was a light yellowish. At 5 p. m. the pupa 
was perfectly formed and dark brown all over, its dimensions now being 
5 mm. in length and 2 mm. in diameter. The larva pupated under the 
thin folds of the outer bark, as there was nothing else in the vial. 
THE PUPA 1 
The pupa (PI. LXI, fig. 2) is of the usual cylindrical type and dark 
reddish brown in color, averaging from 4 to 5 mm. in length by 2 mm. 
in diameter, and is formed by the shrinking of the larval skin. The 
anterior spiracles are slightly more prominent than the posterior pair. 
The pupa of the species was discovered and first shown to the writer by Mr. T. E. Snyder. 
