vn] WATER-SPIDERS 49 



sea water they are quite helpless and soon drown. On 

 the other hand one observer found that a species of 

 Desis was quite at home in a sea- water tank, in which 

 it swam freely and even attacked and fed upon a small 

 fish. Possibly different species of the genus behave 

 in different ways, some being more truly aquatic than 

 others, though it is certain that the troubled waters 

 of a coral sea are not a very promising field for sub- 

 aqueous operations. We know a great deal more of 

 the mode of life of those Agelenids which have taken 

 to living in fresh water. Indeed the subject of the 

 water-spider, Argyroneta aquatica, is so hackneyed 

 that in dealing with it we shall probably be telling 

 the reader much of what he knows already, but that 

 possibility must be risked. 



There is, then, in many of our lakes, ponds and 

 slow-flowing rivers with a weedy bed, a spider which 

 has entirely taken to a water life, and for which it is 

 useless to search on land. It is a docile captive, and 

 consequently a favourite subject for transference to 

 an aquarium, where its habits can be observed at 

 leisure. Its first care is to construct beneath the 

 water a small dome-shaped web, open below, and it 

 generally selects the under surface of the leaf of 

 a water weed for the purpose of anchorage, though a 

 ready-made shelter is often furnished by the empty 

 shell of some fresh-water mollusc. Its next proceeding- 

 is to fill this retreat with air in a very ingenious manner. 



w. s. 4 



