50 SPIDERS [CH. 



While swimming about in the water the spider 

 has a most striking appearance, its abdomen almost 

 resembling a globe of quicksilver. This is because 

 the body is enveloped in a bubble of air, retained 

 largely by the long hairs with which it is clothed. 

 Thus it carries its atmosphere about with it, and as 

 often as not it swims with its back downwards, which 

 has the effect of bringing the bulk of the air-bubble 

 towards its ventral surface, where the breathing pores 

 are situated. Xow when the dome-shaped web is 

 ready to be filled with air the spider rises to the 

 surface, lifts its abdomen above it, and brings it down 

 with a flop, thus imprisoning an extra large air-bubble 

 which it embraces with its hind-legs by way of holding 

 it more securely, and then, swimming rapidly down 

 by means of its other legs to the web it discharges its 

 load of air beneath the downwardly directed mouth 

 of the dome. 



By a frequent repetition of this process the dome is 

 at length filled and converted into a veritable diving- 

 bell, in which the spider can exist quite comfortably 

 until the supply of oxygen in the imprisoned air is 

 exhausted and has to be renewed. From this base 

 it issues forth to feed upon fresh-water insects 

 and crustaceans, sometimes even attacking small 

 fishes. 



The proceedings of the male Argyroneta in the 

 mating season are very curious. He seeks out the 



