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the cases are in some instances prettily curved; these are made 
of fine sand. Some larvae arrange their materials of stick or 
straw transversely; others employ the same materials, but 
arrange them longitudinally. I am of opinion that, as a rule, 
each species of Pliryganeidcn arranges its materials according 
to a uniform pattern, but that numerous exceptions occur in 
this particular, depending upon a change of locality. A species, 
for instance, that dwells in the almost still pools under the 
banks of a rivulet, would form its case of light materials ; but 
if the same caddis-worm were to be deprived of its house, and 
placed in the current of a gently running stream, it is very 
likely that the larva would build a heavier dwelling-house, 
suitable to the change in its position. Various experiments 
have been tried on the caddis-worms, with a view to ascertain 
the materials they would make use of in the construction of 
their houses, and the modes of employing them. In the In- 
tellectual Observer” (vol. v. p. 307-317), the reader will find 
a very interesting account, by Miss Smee, of caddis habitations. 
The authoress, after denuding some worms of their cases, 
placed in the vessel of water which contained them various 
materials, such as coloured glass, cornelian, agate, onyx, brass 
filings, coralline, tortoiseshell, which the worms were able to 
convert to their architectural purposes ; figures of several of 
these artificially constructed cases may be seen in the plate 
which acccompanies Miss Smee’s account. 
Some writers have maintained that when the case becomes 
too small for the larva, it quits it and forms a new one ; but 
M. Pictet says that it adds fresh materials of an enlarged 
diameter at the aperture, cutting off a portion of the opposite 
end. The larvae of the Phryganeidce differ slightly, according 
to the species to which they belong; in general appearance 
they are of a cylindrical form, fat and fleshy, a delicate 
mouthful, no doubt, for a hungry fish ; the cases they inhabit 
are a protection to their naked body, and save them from 
becoming the prey of many fish. • A voracious trout, however, 
does not scruple to swallow house and tenant together. I have 
frequently found the debris of their habitations in the shape of 
gravel and bits of wood in the stomachs of trout. The head is 
firm and horny, with strong mandibles, often notched at the 
tips. The larvae have no antennae. The eyes are small, and 
apparently composed of points at the side of the head, without 
reticulations. The thorax consists of three segments, each of 
which carries a pair of legs ; those of the anterior segment, or 
prothorax, are shorter and stronger than the others. In some 
of the members of this family, as in the PhryganecB proper, one 
notices between the anterior pair of legs a small conical pro- 
jection, or horn, which Keaumur thought was a spinneret; but 
