220 



Aquatic Organisms 



case, differs strikingly in being covered with an 

 abundance of forking filamentous gills which sur- 

 round the body as with a whitish fringe. It feeds, often 

 in some numbers, on the under side of leaves of the white 

 water-lily, or about the sheathing leaf bases of the 

 broad-leaved pond weeds {Potamogeton). 



Elophila fulicalis lives on the exposed surfaces of 

 stones in running streams, dwelling under a silt-covered 

 canopy of thin- spun silk, about the edges of which it 

 forages for algas growing on the stones. Its body is 



Fig. 128. Larva of Elophila 



depressed, and its gills are unbranched and in a 

 double row along each side. It spins a dome-shaped 

 cover having perforate margins under which to pass 

 the pupal period. It emerges, to fly in companies of 

 dainty little moths by the streamside. 



All these aquatic caterpillars like their relatives on 

 land, are herbivorous. They are all small species; 

 they are of wide distribution and are often locally 

 abundant. 



The beetles (order Coleoptera) are mainly terrestrial, 

 there being but half a dozen of the eighty-odd families 

 of our fauna that are commonly found in the water. 

 Both adults and larvae are aquatic, but, unlike the bugs, 

 the beetles undergo extensive metamorphosis, and 



