ARACHNIDA. 



195 



entrance is to be obtained, no other animal can find its 

 way into her impenetrable abode. 



Another species is mentioned by Dr. Johnston, whose 

 habits are still more singular. This spider lives habitually 

 in and under water, but having no fellowship with that 

 element, in which, of course, it cannot breathe like 

 aquatic animals, in order that it may pass its life there in 

 a dry and comfortable manner, appropriates to its use the 

 old shells of water-snails (JjimnoBus stagnalis). Entering 

 the shell, the spider closes the aperture with a web or 

 curtain of varnished silk, which repels the water and 

 hinders its admission ; she then fills her abode with atmo- 

 spheric air. The shell is sometimes found lying at the 

 bottom of the pond, but, rendered buoyant by the air 

 within it, often rises and floats on the surface, and the 

 wily spider is, in this manner carried within reach of her 

 prey, who feel no alarm at the approach of what seems to 

 be a snail. 



The Spiders (properly so called), ( Aranea) belong to this group ; 



FlG. 155. NEST OF HOUSE-SPIDEE. 



they build their webs in the interior of houses, in the angles of walls, 



K 2 



