As a matter of fact, this strange catholicity of diet might well be only apparent. When the Cicadella punctures this or that herb, of whatever species, all that she does is to extract an almost neutral liquid, just as the roots draw it from the soil; she does not admit to her fountain the fluids worked up into essential principles. The liquid that trickles forth under the insect’s gimlet and forms a bead at the bottom of the foamy mass is perfectly clear. I have gathered this drop on the spurge, the arum, the clematis and the buttercup. I expected to find a fire-water, pungent as the sap of those different plants. Well, it is nothing of the kind; it lacks all savour; it is water or little more. And this insipid stuff has issued from a reservoir of vitriol. If I prick the spurge with a fine needle, that which rises from the puncture is a white, milky drop, tasting horribly bitter. When the Cicadella pushes in her drill, a clear, flavourless fluid oozes out. The two operations seem to be directed towards different sources. How does she manage to draw a liquid that is clear and harmless from the same barrel whence my needle brings up something milky and burning? Can the Cicadella, with her instrument, that incomparable alembic, divide the fierce fluid into two, admitting the neutral and rejecting the peppery? Can she be drawing on certain vessels whose sap, not yet elaborated, has not acquired its final virulence? The delicate vegetable anatomy is helpless in the presence of the tiny creature’s pump. I give up the problem. When the Cicadella is exploring the spurge, as frequently happens, she has a serious reason for not admitting to her fountain all that would be yielded by simple bleeding, such as my needle would produce. The milky juice of the plant would be fatal to her. I gather a drop or two of the liquid that trickles from a cut stalk and instal a Cicadella in it. The insect is not comfortable: I can see this by its efforts to escape. My hair-pencil pushes the fugitive back into the pool of milk, rich in dissolved rubber. Soon this rubber settles into clots similar to crumbs of cheese; the insect’s legs become clad in gaiters that seem made of casein; a coating of gum obstructs the breathing-valves; possibly also the extremely delicate skin is hurt by the blistering qualities of the milky sap. If kept for some time in that environment, the Cicadella dies. Even so would she die if her gimlet, working simply as a needle, brought the milk of the spurge to the surface. A sifting takes place then, which allows almost pure water to issue from the source that gives the wherewithal for making the froth. A subtle exhaustion-process, whose mechanism is hidden from our curiosity, a piston-play of unrivalled delicacy, effects this marvellous work of purification.