The Inhabitants of the Aquarium 299 



small stones, little shells and parts of aquatic 

 plants. These the larva joins in such a 

 manner that the result of its labor resem- 

 bles very closely the bottom of the pond or 

 stream in which it lives. As soon as the 

 larva leaves the egg it will surround itself 

 with some small bits of the material closest 

 at hand, later extending the covering in 

 proportion to its own growth. While it has 

 been observed to feed on plants only, some 

 authors claim that it also feeds to a large 

 extend on fish spawn, so that in years when 

 it appears in millions, as frequently happens, 

 the damage it does in fish ponds is said to 

 be very considerable. After having finished 

 its growth, the larva forms into the chrysalis, 

 using the case as a protection, from which, 

 after a short time, the perfect insect emerges. 

 As the case worm is perfectly harmless 

 in any aquarium not devoted to breeding 

 purposes, it can be kept without any risk 

 whatever. 



Water Scorpion or Water Walking-stick 



