Everyday common-sense, expressed in proverbs, tells us over and over again that necessity is the mother of invention. This great truth, which we have learnt by personal experience, we shall learn once more from the Ant-hunter. But first let us give him a name, to simplify our story. Naturalists call him the Ant-lion, a very happy term, which reminds us that, like the Lion, he lives by carnage, slaughtering live prey, in this case Ants. Now that we have christened him we can go on. When he wants his dinner, the Ant-lion says to himself: "You're a fat little beggar, you know, short-legged and slow-moving; you'll never catch Ants by running after them. On the other hand, you can walk backwards, that's capital; you have a head flattened like a navvy's shovel, that's first-rate; your pincers are long and grip like a knife, that's perfect, absolutely perfect. We'll use that talent for walking backwards; we'll use those tools, the shovel and tongs; we'll make craft take the place of the agility which we lack; and the dinner will come along." No sooner said than done. In a nice dry spot, warmed by the sun and sheltered from the rain by an overhanging rock, the wily animal selects a place where Ants are incessantly moving to and fro on household matters. Gravely, with the mathematical accuracy of an engineer tracing the foundation of a well-planned building, the Ant-lion walks backwards, with his body dug into the sand; he turns and turns and in this way hollows out a groove shaped like a perfect circle. Then, still moving backwards and still digging deeper and deeper into the sand, he repeats the circuit many times over, but gradually coming nearer the centre, where he arrives in the end. If any obstacle, such as a large bit of gravel, which would spoil the work, makes its appearance, the Ant-lion takes it on his flat head and, with a vigorous jerk of his neck, flings it to a distance over the edge of the hole. We should use a shovel in exactly the same way to throw out the rubbish when digging. [Illustration] The result of this labour is a sort of funnel, two inches wide and a little less in depth. For that matter, each Ant-lion scoops himself out one proportioned to his size: the larger ones, the giants of the family, produce one almost big enough to hold an orange; the younger and smaller ones are content with a hollow which a walnut would fill. But, whether great funnels or modest dents, all these cavities are constructed on one and the same principle: the slope is very steep and formed of extremely loose sand; nothing, however light, can set foot upon it without producing a landslip, followed by a headlong fall.