How Animals Work. 



and shallow, slow-moving streams which it frequents. 

 That it can live this aquatic life is due to the fact that 

 the long hairs with which its abdomen is densely clothed 

 retain an air bubble when it plunges beneath the water, 

 so that the spider carries its own supply of air to the 

 depths below. Running over the surface of the float- 

 ing leaves, the Water Spider does not attract one's atten- 

 tion particularly, for she looks just a sooty brown, rather 

 compactly built spider ; but the moment she dives 

 beneath the surface her whole appearance changes, and 

 her body looks as if it had suddenly been converted 

 into a globule of quicksilver. At some distance below 

 the surface the Water Spider forms her nest. Her 

 operations are difficult to follow at first, for even in 

 an aquarium, where she will make herself quite as 

 much at home as if she were in her favourite pond, the 

 threads she spins are so fine that it is only when the 

 light strikes upon them at a certain angle that they 

 become visible. Consequently, did we not know what 

 business she is engaged upon as she travels from branch 

 to branch of water weed and back again, we might 

 easily think that she was simply wandering about in a 

 rather feckless sort of way. This is not the case, how- 

 ever, for the spider is really laying down the foundation 

 lines and guide ropes of her nest. Working diligently, 

 she weaves with finest silk a perfect little domed nest, 

 about the size and rather the shape of a large thimble. 

 Her weaving satisfactorily accomplished, the spider next 

 proceeds to bring down a supply of air to fill the nest. 

 Up she mounts in the water, and, raising her abdomen 

 above the surface of the water for an instant, jerks it 

 down again quickly, so as to carry with it a bubble of 



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