Limpet-shaped Shelters 



373 



antennae 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. 



Of ten they occur 



so commonly as , 



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



tO almost COVer attached to a stone in running water. 



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

 showing diatom rake. 



