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 HtUe 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. h\ 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 Irom 

 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 Limnaea, 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 

 Limnsea 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 tne 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 



