The first Cicada appear at midsummer. In the much-trodden, sun-baked paths I see, level with the ground, [[29]]round holes about the size of a man’s thumb. Through these holes the Cicada-grubs come up from the underground to be transformed into full-grown Cicadæ on the surface. Their favourite places are the driest and sunniest; for these grubs are provided with such powerful tools that they can bore through baked earth or sandstone. When I examine their deserted burrows I have to use my pickaxe.
The first thing one notices is that the holes, which measure nearly an inch across, have absolutely no rubbish round them. There is no mound of earth thrown up outside. Most of the digging insects, such as the Dorbeetles for instance, make a mole-hill above their burrows. The reason for this difference lies in their manner of working. The Dorbeetle begins his work at the mouth of the hole, so he can heap up on the surface the material he digs out: but the Cicada-grub comes up from below. The last thing he does is to make the doorway, and he cannot heap rubbish on a threshold that does not yet exist.
The Cicada’s tunnel runs to a depth of fifteen or sixteen inches. It is quite open the whole way. It ends in a rather wider space, but is completely closed at the bottom. What has become of the earth removed to make this tunnel? And why do not the walls crumble? One would expect that the grub, climbing up and down with [[30]]his clawed legs, would make landslips and block up his own house.
Well, he behaves like a miner or a railway-engineer. The miner holds up his galleries with pit-props; the builder of railways strengthens his tunnel with a casing of brickwork; the Cicada is as clever as either of them, and covers the walls of his tunnel with cement. He carries a store of sticky fluid hidden within him, with which to make this plaster. His burrow is always built above some tiny rootlet containing sap, and from this root he renews his supply of fluid.
It is very important for him to be able to run up and down his burrow at his ease, because, when the time comes for him to find his way into the sunshine, he wants to know what the weather is like outside. So he works away for weeks, perhaps for months, to make a funnel with good strong plastered walls, on which he can clamber. At the top he leaves a layer as thick as one’s finger, to protect him from the outer air till the last moment. At the least hint of fine weather he scrambles up, and, through the thin lid at the top, inquires into the state of the weather.
If he suspects a storm or rain on the surface—matter of great importance to a delicate grub when he takes off his skin!—he slips prudently back to the bottom of his snug funnel. But if the weather seems warm he smashes his [[31]]ceiling with a few strokes of his claws, and climbs to the surface.
It is the fluid substance carried by the Cicada-grub in his swollen body that enables him to get rid of the rubbish in his burrow. As he digs he sprinkles the dusty earth and turns it into paste. The walls then become soft and yielding. The mud squeezes into the chinks of the rough soil, and the grub compresses it with his fat body. This is why, when he appears at the top, he is always covered with wet stains.
For some time after the Cicada-grub’s first appearance above-ground he wanders about the neighbourhood, looking for a suitable spot in which to cast off his skin—a tiny bush, a tuft of thyme, a blade of grass, or the twig of a shrub. When he finds it he climbs up, and clings to it firmly with the claws of his fore-feet. His fore-legs stiffen into an immovable grip.
Then his outer skin begins to split along the middle of the back, showing the pale-green Cicada within. Presently the head is free; then the sucker and front legs appear, and finally the hind-legs and the rumpled wings. The whole insect is free now, except the extreme tip of his body.