NORTH AMERICAN CADDIS-FLY LARVZ. 
The Head—Deep mahogany-brown; in some specimens so 
dark that the pattern is visible only in the best illumination, figure 
96. The pattern is very slightly darker than the ground color of 
the head. On the frons, figure 99, the muscle-attachment spots 
are the only marking, but the ground color gradually becomes 
darker toward the mouth-parts. The head, in front of the eyes, 
is without markings; behind the eyes, on the dorsal, ventral and 
lateral surfaces, there is a mottling of small spots, slightly darker 
than the ground color. Each eye is bordered on its lower side by 
a crecentric mark of light color. 
The Thorax.—The pronotum is of lighter color than the head ; 
its pattern is shown in figure 96; on the under-surface there is a 
median dark mark near the caudal margin ; the horn is dark-brown. 
On the mesothorax the dorsal chitinous plate has the same ground 
color as the pronotum. It is bordered along the hind margin by 
a narrow line of deep black, which widens at the angle with the 
lateral margin and extends about half way up the sides; on each 
side of the chitinous plate, opposite the end of the black marginal 
stripe, there is a small, deep, black mark, which sometimes blends 
into the black marginal line; on each side of the median ventral 
line, near the caudal margin of the segment, there is a curved line 
of about five small round chitinous spots. On the dorsal surface 
of the metathorax the median chitinous plates are separated by 
about the breadth of one of the plates; the lateral plates are some- 
what crecentric in form, with a sparse growth of sete on the 
cephalic third ; behind these sete the plates are marked with black. 
The Abdomen.—VYhe dorsal hump on the first segment is well 
developed and pointed—the lateral humps are rounded; on the 
ventral surface there is a broad, raised area covered with an 
evenly-distributed growth of black sete. Each gill arises from 
a single stem and branches biramously on a single plane, figure 
98. The distribution of gills is diagrammed in figure 100. 
DESCRIPTION OF THE CasE.—The typical case of the larva, 
figure 101, is made in the form of a slightly-curved cylinder, taper- 
ing gradually toward the caudal end. On the outside of the curve 
of the cylinder, at the cephalic end, there is a tapering hood which 
extends over the head of the larva, completely covering all but 
the legs. These cases are made of grains of coarse sand of nearly 
uniform size, and are lined with a tough, but brittle, sheet of silk. 
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