3 7 4 LAKES AXD STREAMS 



holoserieea) is another species living on aquatic plants on the hanks of ponds and 

 streams, but in autumn under dry leaves. About a quarter of an inch in length, it 

 is of a uniform greenish colour, except on the back, which is covered with soft, 

 silky hairs. Of the same size is one of the wolf -spiders (Lycosa saccata), which 

 lives on the shores of ponds and rivers and other damp spots. In colour it is 

 brown shading into black, with a long yellowish white stripe on the hind part of 

 the body, and a streak of the same colour on the thorax, the legs being ringed with 

 varying bars. The female may often be noticed as she carries a cocoon attached 

 to her spinneret. 



Crustaceans are well represented in inland water by the cravfish 



(Astacus, or Potainobia,jiv viatilis), which lives in holes on the banks, 



or under stones, and seeks its prey at night, devouring in preference dead animals, 



such as fishes, snails, and worms. The females are distinguished from the males by 



THK CH.VYFISH. 



the smaller claws and broader tail, and the presence of four curved styles on the 

 first two rings of the latter. Both sexes are greenish or brownish in colour, but 

 in rare cases may be blue or red, and when cooked nearly always turn red. They 

 are found in rivers flowing from calcareous ground, and never in granite districts : 

 and their favourite haunts are those parts of the rivers which flow north and south 

 ami yield more shade than those running east and west. They cast their skin two 

 or three times during the hist year, and afterwards annually ; after this process 

 they are for some time soft, and are then called butter-crayfish: in winter they live 

 in holes in the banks and in burrows they make for themselves in streams liable to 

 freeze. The burrows may be more than a yard deep. When the soil is peaty, they 

 work their way into it in all directions, and are often dug out at some distance from 

 the banks. In general appearance they are of the same character as lobsters or 

 prawns. They feed on anything animal or vegetable, living or dead, even on the 

 weaker members of their own species. In size they measure about 4 inches, but 



