122 The Under-Water World 



in marsh mosses ; others again inhabit 

 the sea-shore and are covered by each 

 tide. The " half-way " insects belong to 

 many widely different families ; spring- 

 tails, flies, beetles, etc., are to be found, 

 all leading a life from which it is 

 but an easy step to a pure aquatic 

 existence. 



Although the Water Spider is not 

 strictly an insect, but belongs to the 

 class Arachnida, it seems not out of 

 place to include it in this chapter as it 

 is so frequently found associated with 

 aquatic insects. It is a great favourite 

 with those* who keep small aquaria. 

 Argyroneta aquatica is a moderate-sized 

 spider of about half an inch in length, 

 and lives in ponds and ditches. The 

 abdomen is very thickly covered with 

 short hair. This hair coat retains a 

 covering of air after the spider has 

 visited the surface of the water and gives 

 the body the silvery appearance that is 



