236 
STRANGE DWELLINGS . 
to a point, like an elephant’s tusk. There are also examples of 
mixed structures, where the Caddis has combined shells with 
the leaf and twig cases, and in one of these instances, the little 
architect has bent back the valves of a small mussel, and fastened 
them back to back on its house. Beside these, there are one 
or two very eccentric forms, where the Caddis has chosen some 
objects which are not often seen in such a position. The seed- 
vessels of the elm are tolerably common, but I have several 
specimens where the Caddis has taken the operculum of a dead 
Pond-snail and fastened it to the case ; and there is an example 
where the chrysalis of some moth, apparently belonging to the 
genus Porthesia, has been blown into the water from a tree over- 
hanging the stream, and seized upon by a Caddis as an unique 
ornament for its house. These latter examples were found in a 
stream in Wiltshire, and the tusk-like sand-cases were found in 
a disused stone quarry in the same county. \ 
In this remarkable sub-aquatic home the Caddis larva lives in 
tolerable security, for the head and front of the body are clothed 
in horny mail, and the soft, white abdomen is protected by the 
case. The food of the Caddis is generally of a vegetable -nature, 1 
though there are one or two species which live partly, if not 
entirely, on animal food. When the larva has lived for its full 
period, and is about to change into the pupal condition, it closes 
the aperture of its case with a very strong net, having rather 
large meshes, and lies securely therein until it is about to change 
into the winged state. It then bites its way through the net 
with a pair of strong mandibles, comes to the surface of the | 
water, breaks from its pupal envelope, and shortly takes to flight. 
leaving the pupal skin, but the smaller merely stand on the cast 
skin, which float raft-like on the water. f 
There are one or two species whose cases are not movable, i 
but are fixed to the spot whereon they were made. In order, 
therefore, to compensate for the immovability of the case, the j 
larva has a much larger range of movement. In the ordinary 
species, the creature holds itself to the extremity of the case by 
means of hooks at the end of its body, which can grasp with S 
