Dropsical though it be, the larva cannot carry sufficient liquid to moisten and turn into compressible mud the long column of earth which has to be tunnelled. The reservoir becomes exhausted and the supply has to be renewed. How is this done and when? I think I see. The few wells which I have laid bare throughout their length, with the painstaking care which this sort of digging demands, show me at the bottom, encrusted in the wall of the terminal chamber, a live root, sometimes as big as a lead-pencil, sometimes no thicker than a straw. The visible part of this root is quite small, barely a fraction of an inch. The rest is contained in the surrounding earth. Is the discovery of this sort of sap fortuitous? Or is it the result of a special search on the larva’s part? The presence of a rootlet is so frequent, at least when my digging is skilfully conducted, that I rather favour the latter alternative. Yes, the Cicada-grub, when hollowing out its cell, the starting-point of the future chimney, seeks the immediate neighbourhood of a small live root; it lays bare a certain portion, which continues the side wall without projecting. This live spot in the wall is, I think, the fount from which the contents of the urinary bladder are renewed as the need arises. When its reserves are exhausted by the conversion of dry dust into mud, the miner goes down to his chamber, drives in his sucker and takes a deep draught from the cask built into the wall. With his jug well filled, he goes up again. He resumes his work, wetting the hard earth the better to flatten it with his claws and reducing the dusty rubbish to mud which can be heaped up around him and leave a clear thoroughfare. That is how things must happen. So logic and the circumstances of the case tell us, in the absence of direct observation, which is not feasible here. If this root-cask fail, if moreover the reservoir of the intestine be exhausted, what will happen then? We shall learn from the following experiment. I catch a grub as it is leaving the ground. I put it at the bottom of a test-tube and cover it with a column of dry earth, not too closely packed. The column is nearly six inches high. The larva has just quitted an excavation thrice as deep, in soil of the same nature, but offering a much greater resistance. Now that it is buried under my short, sandy column, will it be capable of climbing to the surface? If it were a mere matter of strength, the issue would be certain. What can an obstacle without cohesion be to one that has just bored a hole through the hard ground?