NORTH AMERICAN CADDIS-FLY LARVZ. 
end the sand of the tube is cut away in semi-circular form and the 
opening thus formed is covered with a lattice-like arrangement 
of heavy rods of silk, figure 119. This end of the case is held 
above its support by a short stalk of silk. At the caudal end of the 
case a semi-circular opening is not made, but the lattice-like silk. 
rods are made between the end rock and the ventral surface of the 
tube. Usually the rods are overlapped by the edges of the case 
and are invisible from the outside. 
During the long prepupal period, lasting several months, from 
late spring until the latter part of August, the larve remain quiet 
with their heads folded between their legs. During this period 
they are incapable of taking any food, and dissection shows the 
alimentary canal entirely void of material of any kind. 
If, during this period of helplessness, the stream recedes enough 
to dry the cases, the larve perish, unable to reach the water, which 
may be but a fraction of an inch below. 
Preriop oF EmERGING.—Adults emerge about the end of the 
first week of October, and continue on the wing until the middle 
of November. They are weak flyers and do not wander far from 
the stream’s edge. 
Description oF Larva.—Length (in natural position, with 
head turned under thorax), 8—1o mm. 
Head.—In form, the head, figure 115, is long and tapering 
from the eyes to the mouth parts, and quite abruptly rounded be- 
hind the eyes. The frons, figure 116, seen in profile, has a de- 
cided mound-like prominence at the point between the two eyes. 
In color, the dorsal surface of the head bordering the frons is 
dark-brown, almost black on the cephalic portion, but becoming 
lighter as it progresses back; the frons is dark-brown, except an 
irregular mark of light color, figure 116; behind the dark mark 
bordering the frons the head is irregularly spotted with light- 
brown; the sides of the head are light-brown, except a narrow 
area surrounding each eye, which is almost white; on the under 
side of the head there is a broad mark of brown, which gradually 
shades into the light color of the sides, except along the cephalic 
margins, where it is narrowly connected with the dark color of 
the dorsal surface. 
Thorax.—The prothorax above, figure 115, is light straw color, 
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