WATER SPIDERS. 271 



WATER SPIDERS. 



Under the present head I rank two members of 

 the Arachnida : one a trespasser in, and the other 

 upon, the water. 



The first of these creatures is the Water Spider 

 (Argyronetra aquatica) , a being which affords another 

 of the many examples in which nature has preceded 

 the art of man. In the rat-tailed fly we have already 

 seen that the diving machinery of modern days has 

 been anticipated by the elongated air-tube of the 

 larva, and in the present case we have an exact 

 analogy with the diving-bell itself. I will first give a 

 brief account of the habits of the Water Spider, and 

 then show the analogy between its habitation and 

 the diving bell. 



I must premise, in the first place, that the Water 

 Spider has the power of swimming and diving, and 

 that it obtains its prey in the water. If any ordinary 

 land spider be thrown into water, it will float for a 

 considerable time, being buoyed up by the numerous 

 air-bubbles which are entangled among the hairs 

 of its body. The Water Spider, in addition to this 

 airy envelope, can carry with it a large bubble of 

 air, which is sufficient for its respiration for some 

 little time. 



I have often watched the Spider take its bubble 

 beneath the water. It comes to the surface, and waits 

 there for a moment or two, as if to collect its forces. 

 It then gives a sort of jerk of the body and kick of 



