TR1CHOP TER A. 
I89 
it lives. Very little respect for the architectural skill of 
these builders is commanded by their rude dwellings. But 
if one 'ooks a little farther, something will be found that is 
Sure to excite admiration. The dweller within this rude re¬ 
treat is a fisherman ; and stretched between two stones near 
by can be seen his net. This is made of silk. It is usually 
funnel-shaped, opening up-stream; and in the centre of it 
there is a portion composed of threads of silk extending in 
two directions at right angles to each other, so as to form 
meshes of surprising regularity. It is as if a spider had 
stretched a small web in the water where the current is the 
swiftest. These nets occur in rapids between stones, but in 
many places they are to be found in greater numbers along 
the brinks of falls. Here they are built upon the surface of 
the rock, in the form of semi-elliptical cups, which are kept 
distended by the current. Much of the coating of dirt with 
which these rocks are clothed in summer is due to its being 
caught in these nets. We have not yet observed the owners 
of the nets taking their prey from them ; but we cannot 
doubt that they are made to trap small insects or other ani¬ 
mals that are being carried down-stream ; for the larvae of 
the sub-family to which these net-builders belong, the Hy- 
dropsychince y are known to be carnivorous. It should be 
noted here, however, that the greater number of Caddice- 
worms are herbivorous. 
When a Caddice-worm gets ready to change to a pupa it 
retires into its house and builds a door to keep intruders 
out; but the door always has an opening to allow the water 
to flow in so that the pupa can breathe. Sometimes a simple 
grating of silk is made over the entrance. 
On one occasion the writer had the good fortune to ob¬ 
serve a Caddice-fly leave the water and take its first flight. 
The specimen was one of the net-building species, Hydrop¬ 
syche (Hy-drop-sy'che), which I was breeding in an aquarium 
in my laboratory. It swam to the surface of the water 
repeatedly, using its long middle legs. When swimming, 
