Leaf-drifts 



361 



surface and burrowing mayflies in the beds, and a con- 

 siderable variety of the lesser midges on every possible 

 support. 



Fig. 216. A bit of the bed of a pool in a woodland stream, show- 

 ing among the forest Utter the wooden cases of the larva of the 

 ca.ddis-fiy, Halesus giiUifer. (See also fig. 104 on p. 198). Pro- 

 tective resemblance. There are 14 cases in the picture. 



