CH. XV.] THE CATERPILLAR. 263 



the friction to which it is unavoidably exposed from 

 the movements of the insect. 



Although the vestments of each tribe are gene- 

 rally formed in a uniform manner, still there are 

 some exceptions to this ; for instance, the caddis- 

 worm, so well known to old Isaak Walton, and to 

 all the brothers of the angle, is not at all choice in 

 the selection of the ornaments with which it deco- 

 rates its coat : shells, stems, leaves, straws, and bits 

 of wood, in short, almost any manageable substance, 

 will serve its purpose. The only thing which is 

 common to all the figures is, the cylindrical tube 

 opens at each extremity. 



1. In figure 1, the worm has covered its silken case with leaves, so 

 arranged as to present the appearance of a Spanish mantle. 



2. In fig. 2, it is bristled all over with stalks of plants, surmounted by 

 a huge shell, and two pieces of wood, looking very much like horns. 



3. In fig. 3, the worm is seen cased in two semi-cylindrical pieces of 

 hollow bark ; having accidentally lighted upon these materials, it 

 has joined them together, and has thus formed a complete covering 

 with little or no sewing. 



4. Fig. 4 represents the worm enveloped in a symmetrical and spiral 

 case of riband beautifully rolled ; the parts are so nicely fitted, that 

 it has the appearance of being one continuous piece ; a careful ex- 

 amination will, however, show, that it is composed of several de- 

 tached bits joined together. 



5. The last, fig. 5, exhibits a section of one of those cases, with tha 

 bits of wood arranged around it. 



Sometimes these coats are covered exclusively 

 with shells, which occasionally envelope living snails, 



