Yet sandhoppers have so many enemies that it really seems wonderful that any of them should be left alive at all. Nearly all the shore birds feast upon them, and so do many of the land birds. Indeed, when the tide is rising, you may often see a long line of birds standing closely side by side together a few feet in front of the water’s edge and gobbling up the active little creatures in thousands. Then the shore crabs are very fond of them, and destroy thousands more. And even when they are buried deeply in the sand they are not safe, for there is a little beetle which goes down their burrows after them, and catches and eats them there very much as a ferret catches a rabbit in its hole.
But it is just as well that they do not all get eaten, for sandhoppers are very useful little creatures indeed. They feed upon the masses of decaying sea-weed which are constantly flung up on the shore by the waves. For they, too, belong to the great army of “Nature’s Dustmen,” like the “zoeas” of the crabs and lobsters, and help to clear away all kinds of rubbish which would poison the air and the water if it were left to decay. Indeed, they will eat almost anything, and if you were to tie up a number of sandhoppers in your handkerchief, and leave them there for a few minutes, you would never be able to use the handkerchief again; for you would find that their sharp little jaws had nibbled it into holes.
If you watch a sandhopper carefully when it is skipping about, you will find that it leaps by doubling its body up, and then straightening it out again with a sudden jerk.
1. SANDHOPPER (enlarged).2. SAND SCREW (enlarged).
1A. ” (life-size). 2A. ” (life-size).
PLATE XXIX
THE SAND SCREW (2 and 2 A)
If you follow the tide as it goes out on a still day, you will notice that it leaves the sand quite smooth behind it. But if you come to the same spot about half-an-hour later, you will often find that it is marked by numbers of winding tracks, which look just as if they had been made by worms. These, however, are the work of the Sand Screw, a curious little creature which in many ways is very much like a sandhopper. But instead of sinking its burrows almost straight downwards into the sand, as sandhoppers do, it drives them along almost as a mole does, just below the surface.