Yes, May, this little cast is made of chitin, and it will last a long time. Chitin is a very indestructible substance; even fire will not destroy it, but in course of time the moisture and the acids in the earth destroy it, so that at last the millions of cicada shells and grasshopper cast-off skins, which are also of chitin, and cricket moults, and all the other little cast-aside chitinous overcoats of the insects, return again to the earth and the air whence they came. The minerals and gases that compose them let go of each other, as it were, and the chitin is no longer chitin. Amy says she has seen these little cicada shells hundreds of times but did not know what they were. Yes, we are sure to find them almost every summer. If we look, we will also find other larvae shells. Down in the grass are the cast-off coats of the grasshoppers and the crickets. All we need do is to look, and we shall be sure to find them--like unsubstantial ghosts of the active little wearers. No doubt you all have heard of the seventeen-year locusts. They, too, are cicadas, and they look very much like this one, only it takes the young ones seventeen years to complete their growth. Think of living in the ground and sucking the juices out of the earth and of tree roots for seventeen years! [Illustration] How would you like to do it? But no doubt the cicada is quite happy living in this way. At the end of seventeen years the cicadas come up out of the earth in great swarms. They cast their skins for the last time. The queer little shells are seen everywhere, and the air resounds with the songs of the freed prisoners. In the South it takes only thirteen years for these cicadas to develop. [Illustration] I once went up the side of a beautiful mountain in North Carolina, where was such a mighty host of cicadas in the trees that I could not hear my companion speak, and a little way off the noise sounded like a torrent of rushing water. THE ODD SPITTLE INSECT Why, little Nell! What is the matter? You do wish the frogs would stop spitting on the grass? Let me see; why, poor child, she is all covered with frog spittle. That is kind, Ned. See, he is wiping her apron off with some fresh, clean leaves. Let us rest awhile under this shady tree. John, pick that grass blade with the frog spittle on it. Be careful not to disturb it. [Illustration] There is a surprise in store for you; this white frothy substance that is so abundant in some places in the summer and that looks like spittle is--guess what? Frog spittle, May says. So you think the frogs spit on the grass do you? They must be tall frogs to reach up so high. With this little twig let us carefully brush away the white froth. Now see. Yes, there is something in the centre of it. It is the larva of a--bug! [Illustration]