THE CADDIS FLY. 
235 
of bark from the plants. Next comes a series of cases in which 
the Caddis larva has contrived to secure a great number of 
cylindrical grass stems and arranged them transversely in several 
sets, making one set cross the other so as to leave a central space, 
in which the little architect can live. One or two cases are 
made wholly of bark, apparently the cuticle of the common reed, 
a plant which is very common in the Cherwell, whence the cases 
were taken. In all probability these strips of cuticle have been 
dropped into the river by the water rats while feeding on the 
reeds. 
Several cases are made entirely of leaves, mostly taken from 
the white-thorn, which grows in great quantities along the banks 
of the above-mentioned river. Then, there are cases which are 
equally composed of sticks and leaves, these materials generally 
occupying opposite ends of the case. There is another series of 
cases made up of fine grass, apparently the debris of hay which 
had been blown into the water during the summer, and having 
the materials laid acoss each other like the needles of a stocking- 
knitter. Most of these cases are balanced by a stone. 
Next come a number of cases which are composed of small 
shells, those of the Planorbis being the most common, and 
having among them a few specimens of the Limnasa, or pond- 
snail, and many separate valves and perfect shells of the fresh- 
water mussel. The Caddis larva is an incorrigible kidnapper, 
seizing on any shell that may suit its purpose, without troubling 
itself about the inhabitant. It is quite a common occurrence 
to find four or five living specimens of the Planorbis and 
Limn sea affixed to the case of a Caddis larva, and to see the 
inhabitants adhering to the plants and endeavouring to proceed 
in one direction while the Caddis is trying to walk in another, 
thus recalling the well-known episode of the Tartar and his 
captor. In these cases the cylindrical body is made of sand and 
small, fragments of shells bound together with a waterproof 
cement, and the shells are attached by their flat sides to the 
exterior. 
There are also several cases which are made entirely of sand 
cemented together, some being cylindrical and others tapering 
