Water is always water, whether it come from the stagnant pool or the clear stream, from a poisonous liquid or a healing infusion; and it possesses the same properties, when it is rid of its impurities by distillation. In like manner, the sap, whether furnished by the spurge or the bean, the clematis or the sainfoin, the buttercup or the borage, is of the same watery nature when the Cicadella’s syphon, by a reducing-process which would be the envy of our stills, has deprived it of its peculiar properties, which vary so greatly in different plants. This would explain how the insect makes its froth rise on the first plant that it comes across. Everything suits it, because its apparatus reduces any sap to the condition of plain water. The inimitable well-sinker is able to produce the limpid from the cloudy and the harmless from the toxic. It may possibly happen that the insect’s well supplies water that is not quite pure. If left to evaporate in a watch-glass, the clear drop that trickles from the mass of foam yields a thin white residue, which dissolves by effervescence in nitric acid. This residue might well be carbonate of potash. I also suspect the presence of traces of albumen. Obviously, the Cicadella finds something to feed on at the bottom of the puncture. Now what does she consume? To all appearances, something with an albuminous basis, for the pigmy herself is, for the most part, but a grain of similar matter. This element is plentiful in all plants; and it is probable that the insect uses it lavishly to make up for the expenditure of gum needed for the formation of froth. Some albuminous product, perfected in the digestive canal and discharged by the intestine as and when the blow-pocket expels its bubble of air, might well give the liquid the power of swelling into a foam that lasts for a long time. If we ask ourselves what advantage the Cicadella derives from her mass of froth, a very excellent answer is at once suggested: the insect keeps itself cool under that shelter, hides itself from the eyes of its persecutors and is protected against the rays of the sun and the attacks of parasites. The Lily-beetle makes a similar use of the mantle of her own dirt; but she, most unhappily for herself, flings off her nasty cloak and descends naked from the plant to the ground, where she has to bury herself to slaver her cocoon. At this critical moment, the Flies lie in wait for her and entrust her with their eggs, the germs of parasites which will eat into her body.