no 



MOLLUSC A, INSECTS, ETC. 



Phryganeida. There are a great many of them, and 

 the larvae of each have usually a different plan of con- 

 structing their well-known tubes, by which they may 

 be identified. Some select minute shells of a species 

 of Planorbis or Pisidium ; others use grains of sand. 

 The genus Limnephilus prefers pieces of rush or other 

 aquatic weeds. But all of them are interesting, and 



Fig. 63. 



Fig. 64. 



Limnephihis flavicornls. 

 Fig. 65. 



Larvse of Phryganea grandis. 



Fig. 66. 



Limnephihis 

 rhombicus. 



Caddis-worm pro- 

 jecting its head out of 

 tube. 



seem to be perfectly aware that they are regarded as 

 choice and dainty bits by other larger and more active 

 water animals. All of them hold on to the interiors 

 of their frail defences by means of a series of hooks, 

 so that it is somewhat difficult to drag them out 

 forcibly. Before they pass into the quiescent state, 

 previous to changing into their image condition, they 

 protect themselves by making gratings at the ends of 

 their tubes. The insects into which these larvae even- 



