loo The Irish Naturalist. 



present pair seemed to have no intention of dying, and soon 

 established themselves in the rock-work of the aquarium, and 

 I had the pleasure of seeing each with a silvery web full of 

 air. I was very curious about this web full of air, for I had 

 been told that there were various theories as to the way in 

 which it was filled, consequently I was much delighted one 

 day at seeing the process. I noticed the smaller of the two 

 spiders going backwards and forwards from a point below to 

 the surface. I^ooking closer, I saw that it had spun a web, 

 and was occupied in filling it with air. It would run up to 

 the surface, fill its air sac, and run dovv'U to its web and empty 

 its cargo of air, and immediately return for more, until the 

 web was fully distended. For some days the two spiders 

 kept their respective quarters, but one morning the smaller 

 had disappeared, and I came to the conclusion that the larger 

 spider had yielded to the worst instincts of its nature, and 

 devoured its companion. I was consequently much surprised 

 and pleased a few days ago, to see the small spider again, after 

 losing sight of it for fully two months. The large spider had 

 left its usual haunt, and the small one was coolly sitting there. 

 It has since disappeared again, so I conclude it ensconces 

 itself in some hole or corner where its bigger brother cannot 

 intrude. 



I was somewhat puzzled at first to understand what use the 

 spiders made of the bags of air which they accumulated, but 

 careful observation revealed the secret. The spider weaves 

 its air-bag in some suitable position, and then sits with the 

 opening of its own air sac in the woven bag of air, and is thus 

 able to remain under the surface for a long time, and pounce 

 upon any unwary denizen of the waters that comes within its 

 reach. When the air in the web is exhausted, the spider does 

 not seem to use the same web again, but to make a new one. 

 Owing to this habit, the hole in which the big spider lives 

 has got quite full of discarded webs. These, of course, are 

 useful for entangling passing insects. Most of the time the 

 spider sits motionless in its web like its congeners who live 

 above water. I was much amused the other day at the big 

 spider. I was poking about with my pincers, and put them 

 near it, when immediatel}^ it made at them in most fierce 

 fashion, and followed them out of its lair up to the surface. It 

 then retreated, but on my putting the pincers down again, it 



