254 NATURAL HISTORY OF AQUATIC INSFXTS CH. 



out of these leaves, and fastened them to its sheath 

 placing some of them transversely in the manner 

 already described. When the outside of the sheath 

 had tiken the desired form, the larva worked at the 

 inside, spinning a silken lining of a substantial kind, 

 I have since seen several larvae of the same species 

 at work, making new sheaths, lengthening or 

 strengthening the old ones, adding new fragments 

 either to increase or diminish its weight, and all that 

 I have been able to see was merely a repetition or an 

 adaptation of the operations just described. [The 

 cases of small stones or sand are the hardest to make, 

 A Caddis-worm will complete one of these in five or i 

 six hours.] 



" In some species (such as Phryganea grandis) the 

 sheath appears to be rolled spirally round, like a i 

 ribbon wound upon a stick. I have seen bits of oak 

 leaf arranged in this way along some very large sheaths i 

 which I found in a pond in the Bois de Boulogne. | 

 Some of these were only covered for part of their Ij 

 length by bits of broad leaves, the rest being occupied [l 

 by narrow strips arranged side by side so as to form \l 

 a spiral band extending to the higher end of the I 

 sheath. The larvae which inhabit these last sheaths 1 

 have two parallel curved bands on the front of the J 

 head. \ 



" The larvae of a very small species [Triaenodes :| 

 bicolor] are also covered by a spiral band, and look 

 as if a green ribbon had been bound round them from ! 

 head to foot. The dress of the larvae is like our own i 

 in one respect ; it is much handsomer when it is new. ,/ 

 The colour changes in time from a beautiful green to 



