66 
NATURE STUDY. 
rising or falling. It is seldom stationary for any great 
length of time, and if it is rising, we shall see, around the 
grasses and rushes standing in it, little depressed rings, 
like the depressions made by the needle and the strider’s 
feet. If the water is falling, there will be a raised ring, 
instead of a depression, around the grasses and rushes. 
Water, whether rising or falling, flowing or at rest, is cov¬ 
ered by what is called a surface film. It is very thin, so 
thin that we can scarcely conceive of it, and yet it has con¬ 
siderable strength and is stretched tightly by what is known 
as surface tension. This film, with the tension or pull 
which holds it stretched over the water, explains many 
things about the action of water and other liquids, and 
among other things that it does it makes a safe floor for the 
strider to walk upon. So we see there is no longer any 
mystery about this queer way of walking. 
The strider lives upon the juices of insects, which he 
catches with his strong fore legs. He has a long, sharp 
beak, with a bristlelike piercer which he can move in and 
out of the beak while boring a hole through the hard cov¬ 
ering of his prey. The beak is hollow, for sucking, and 
when all the fluid in the insect's body has been drawn into 
the strider’s stomach, the empty shell is thrown away, the 
jointed beak is laid back beneath the head and between 
the fore legs, and the water strider rests upon his film floor 
or moves about with long skips or strides, ready for an¬ 
other victim, for his lunches are usually small and he is 
always hungry. 
Some creatures that do not walk upon the water, but live 
in it, often come up and rest by the help of this wonderful 
surface film, and there are others which move along, cling¬ 
ing to its under side. This is another queer way of walk¬ 
ing, and we will see what we can learn about it when we 
go abroad next time for a bit of nature study. 
