Limpet-shaped Shelters 



373 



antennas lives within, and protrudes its pliant length 

 in foraging on the algal herbage that grows about its 

 front door. And 

 there are many 

 other lesser 

 midges whose 

 larvae dwell in 

 silt-covered 

 tubes on rocks 

 in the rapids. 

 Often they oc- 

 cur so commonly 

 as to almost 

 cover the surface. 



Shelters also limpet-shaped It should be noted in 

 passing that this flattened form, which is characteristic 

 of so many members of lotic society, is characteristic 

 not only of the living animals but also of their shelters. 

 The tarpaulin-like web of the moth Elophila fulicalis 

 is flat, and the pupal shelter is quite limpet- 

 shaped. The case of Leptocerus ancylus is widely 

 cornucopia-shaped, its mouth fitted to the stone. The 

 coiled case of Helicopsyche is a very broad spiral, closely 



FIG. 223. Larval cases of the midge, Tanytarsus, 

 attached to a stone in running water. 



FIG. 224. The maxilla of a mayfly, Ameletus ludens, 

 showing diatom rake. 



