ii6 THE WONDER OF LIFE 



than the female. The length of the male's body is about 

 15 mm. and that of the female about 8 mm. The colour 

 is reddish-brown to olive-brown, but it has when swimming 

 a silvery appearance due to bubbles of air which are 

 entangled among the velvety hairs and shreds of silk which 

 cover the body. It is in quiet pools where there are abun- 

 dant water- weeds that this member of a thoroughly terres- 

 trial race makes itself at home. There are a few other 

 spiders, e.g. species of Dolomedes and Pirata, which creep 

 down plants right into the water when danger threatens, and 

 there are a few others which walk daintily on the surface- 

 film, but Argyroneta is the only thoroughly sub-aquatic type. 

 It makes, as every one knows, a dome-shaped web, usuaUy 

 attached by silk threads, like a tent by its ropes, to water- 

 weeds and stones, but occasionally fashioned inside a water- 

 snail's empty shell, or in a hole in a piece of wood. In all 

 cases it fills its dome with air brought down from the sur- 

 face, till the result is something between a diving-bell and 

 a submerged balloon. It has anticipated at least one of 

 man's many inventions, though it is probably but dimly 

 aware of its inherited or instinctive skilfulness. ■ There 

 is no hiat of prentice-work in the web that is made in such 

 peculiar conditions, and it is interesting to notice that the 

 architecture bears a close resemblance to that of the webs 

 made by terrestrial members of the same family. For some 

 reason or other, the pattern worked out in winter is different 

 from that of the summer web. The webs require frequent 

 renewal, for inquisitive Gammarids and the like are con- 

 tinually breaking the moorings. The supply of air has 

 also to be continually renewed. With this work and with 

 the pursuit of the water-insects on which it feeds, the 

 spider is kept busy, but it is able to spare a good deal of 



