90 ARACHNOIDEA, 



CASE surface of the thorax and abdomen. A double row of small 



VII. 



white spots are ranged longitudinally on the back of the abdomen, 

 and the legs are pale red. It is only to be found in fenny or 

 marshy places, and its best known habitat is the fens of Cam- 

 bridgeshire, where its remarkable habits have long been known, 

 Mr. Wood, in his " Homes without Hands," gives the following : 

 Not content with chasing insects on land, it follows them to the 

 water, on the surface of which it runs freely. It needs, however, 

 a resting place, and forms one by getting together a quantity of 

 dry leaves and similar substances, which it gathers into a rough 

 ball and fastens with a silken thread. On this ball the spider 

 sits, and allows itself to be blown about the water by the 

 wind. Apparently, it has no means of directing its course, but 

 suffers its raft to traverse the surface as the wind or current 

 may carry it. 



There is no lack of prey, for aquatic insects are constantly 

 coming up to breathe the air, and although they may only remain 

 on the surface for a second or two, the spider can seize them 

 before they gain the safe refuge of the deeper water. Then 

 there are insects, such as the gnat, which attain their wings on the 

 surface of the water, and can be taken by the spider before they 

 have gained strength for flight. Also there are insects which 

 habitually traverse the water in search of prey, and which are 

 themselves seized by the more powerful and equally voracious. 

 More than this, moths, flies, beetles, and other insects, are con- 

 tinually falling into the water, and these afford the easiest prey to 

 the raft spider, who pounces upon them as they vainly struggle to 

 regain the air, and then carries them back to its raft, there to 

 devour them in peace. The spider does not merely sit upon the 

 raft, and there capture any prey that may happen to come within 

 reach, but when it sees an insect upon the surface, it leaves the 

 raft, runs swiftly over the water, secures its prey, and brings it 

 back to the raft. It can even descend below the surface of the 

 water, and will often crawl several inches in depth. This feat it 



