SERICOSTOMATIDZ. 
Head.—The dorsal surface of the head, figure 124, is dark- 
brown, except along the margins of the frons, where there is a 
very narrow light line which broadens at the constriction of the 
sclerite; there is also a light-colored area in front of the caudal 
margin of the head, and a light circular area surrounding each 
eye. The caudal third of each side of the head has numerous light- 
colored muscle-attachment marks. On the ventral surface the 
head is white, with several conspicuous dark-brown muscle-attach- 
ment marks on each side of the gula. 
The Thorax.—The pronotum, figure 124, is brown, with a 
varying pattern of light and dark marking; on each side of the 
segment the chitinous support for the leg has a deep notch, figure 
127, into which a tongue-like extension of the coxa hinges. 
Abdomen.—On the first segment the dorsal hump is absent, and 
the lateral humps are but slightly raised and are thickly covered 
with minute spines, arranged in pairs. Gills and the lateral fringe 
are absent. The drag-hooks bear several long teeth, figure 126, 
giving each hook a fan-like shape. 
The abdomen is curved to fit the form of the case, as the insect 
lives with its ventral side toward the axis of the whorl. 
DESCRIPTION OF THE CasE.—The well-known spiral case, fig- 
ure 128, quite closely resembles some of the fresh water molluscs, 
for which it has been more than once mistaken and described. It 
is made of minute sand grains, securely cemented together. The 
tube in which the larva lives is broadest at the mouth and tapers 
gradually to the tip. 
Though the molluse-like case of the genus Helicopsyche is a 
unique plan of architecture, it is not such a wide deviation from 
the cases of other Trichoptera as appears on first sight. Ap- 
parently the larva starts its case in somewhat the form of a minute 
horseshoe and, continuing the cephalic end around the caudal end, 
builds on until the spiral form is reached, ever-increasing the di- 
ameter as it builds around the circumference. 
Such a case would be made by a species that makes a cornu- 
copia-shaped dwelling, such as Leptocerus ancylus, figure 167, if 
the bend in its case were very greatly increased and the tube 
slightly elongated. 
Before pupation the case is tightly glued to some solid sup- 
port and the cephalic end is closed by a convex lid of silk, with a 
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