66 POND LIFE 



formance, some will occasionally fall on to their backs, and 

 then will be seen the advantage of long legs. For by carefully 

 manipulating various joints the creature is able to lever itself 

 back to a normal position. 



Like all insects, the Gerridae have three pairs of legs. The 

 first pair are placed on the thorax just below the head, and are 

 held in front with only the first joint resting on the water- 

 film. The second pair are stretched out to the greatest advan- 

 tage, and in this case more than half rests on the water. These 

 legs, which are the oars of the insect, are attached to the lower 

 end of the thorax, and are remarkable for their distance from 

 the fore legs. The third or last pair act as rudders, and are 

 very seldom used in any other way. It is most remarkable 

 that each pair of legs does its particular work only. The last 

 pair, the rudders, steer the course, and are never used for 

 swimming ; and even, when the insect is attempting to escape 

 capture, remain stretched in their usual position. The insect 

 has perfect control of all its legs, but the habit of only using 

 the second pair as swimming organs is so customary that the 

 idea of employing these for any other purpose does not seem to 

 occur, even at the most critical moments, when their use would 

 be of great assistance. 



The pond-skater's head is terminated by a trunk-like organ 

 known as the beak. The under side of its body is covered with 

 close velvety hairs, which, should the insect be submerged, pre- 

 vent the water from reaching its body. But under normal 

 conditions this very seldom occurs, for the healthy insect 

 is most particular to keep its body distant from the water 

 surface. 



Occasionally a pond-skater will take advantage of the wind 

 or of the prevailing current, and will drift without effort for 

 some distance. They seem to have a great liking for herbage, and 

 are only too glad to rest amongst the partly submerged grass. 

 Should they be disturbed they escape on the water-film, and as 

 soon as the cause of the trouble has departed hurry back to 

 their favourite haunts. 



Their eyesight is certainly remarkably keen, and they notice 

 every movement of the clumsy biped, man, even when he 

 is several feet away, and dodge the net with surprising 

 dexterity. 



Pond-skaters spend much of their " free time " brushing their 

 legs and beaks in a somewhat similar manner to a carver 

 sharpening a knife, first doing one side and then the other. 



Their food consists of dead and living insects. Should an 

 unfortunate non-aquatic fly tumble into the water, near to a 



