THE FOAMY CICADELLA

In April, when the Swallow and the Cuckoo visit us, let us consider the fields for a while, keeping our eyes on the ground, as befits the eager observer of insect-life. We shall not fail to see, here and there, on the grass, little masses of white foam. It might easily be taken for a spray of frothy spittle from the lips of a passer-by; but there is so much of it that we soon abandon this first idea. Never would human saliva suffice for so lavish an expenditure of foam, even if some one with nothing better to do were to devote all his disgusting and misdirected zeal to the effort.

While recognizing that man is blameless in the matter, the northern peasant has not relinquished the name suggested by the appearance: he calls those strange flakes “Cuckoo-spit,” after the bird whose note is then proclaiming the awakening of spring. [425]The vagrant creature, unequal to the toils and delights of housekeeping, ejects it at random, so they say, as it pays its flying visits to the homes of others, in search of a resting-place for its egg.

The interpretation does credit to the Cuckoo’s salivary powers, but not to the interpreter’s intelligence. The other popular denomination is worse still: “Frog-spit!” My dear good people, what on earth has the Frog or his slaver to do with it?1

The shrewder Provençal peasant also knows that vernal foam; but he is too cautious to give it any wild names. My rustic neighbours, when I ask them about Cuckoo-spit and Frog-spit, begin to smile and see nothing in those words but a poor joke. To my questions on the nature of the thing they reply:

“I don’t know.”

Exactly! That’s the sort of answer I like, an answer not complicated with grotesque explanations.

Would you know the real perpetrator of this spittle? Rummage about the frothy [426]mass with a straw. You will extract a little yellow, pot-bellied, dumpy creature, shaped like a Cicada without wings. That’s the foam-producer.

When laid naked on another leaf, she brandishes the pointed tip of her little round paunch. This at once betrays the curious machine which we shall see at work presently. When older and still operating under the cover of its foam, the little thing becomes a nymph, turns green in colour and gives itself stumps of wings fixed scarfwise on its sides. From underneath its blunted head there projects, when it is working, a little gimlet, a beak similar to that of the Cicadæ.

In its adult form the insect is, in fact, a sort of very small-sized Cicada, for which reason the entomologist capable of shaking off the trammels of nonsensical nomenclature calls it simply the Foamy Cicadella. For this euphonic name, the diminutive of Cicada, the others have substituted that horrible word Aphrophora. Orthodox science says, Aphrophora spumaria, meaning Foamy Foambearer. The ear is none the better for this improvement. Let us content ourselves with Cicadella, which respects the tympanum and does not reduplicate the foam.[427]

I have consulted my few books as to the habits of the Cicadella. They tell me that she punctures plants and makes the sap exude in foamy flakes. Under this cover, the insect lives sheltered from the heat. A work recently compiled has one curious piece of information: it tells me that I must get up early in the morning, inspect my crops, pick any twig with foam on it and at once plunge it into a cauldron of boiling water.

Oh, my poor Cicadella, this is a bad look-out! The author does not do things by halves. I see him rising before the dawn, lighting a stove on wheels and pushing his infernal contrivance through the midst of his lucern, his clover and his peas, to boil you on the spot. He will have his work cut out for him. I remember a certain patch of sainfoin of which almost every stalk had its foam-flakes. Had the stewing-process been necessary, one might just as well have reaped the field and turned the whole crop into herb-tea.

Why these violent measures? Are you so very dangerous to the harvest, my pretty little Cicada? They accuse you of draining the plant which you attack. Upon my word, they are right: you drain it almost as dry as [428]the Flea does the Dog. But to touch another’s grass—you know it: doesn’t the fable say so?—is a heinous crime, an offence which can be punished by nothing less drastic than boiling water.

Let us waste no more time on these agricultural entomologists with their murderous designs. To hear them talk, one would think that the insect has no right to live. Incapable of behaving like a ferocious landowner who becomes filled with thoughts of massacre at the sight of a maggoty plum, I, more kindly, abandon my few rows of peas and beans to the Cicadella: she will leave me my share, I am convinced.

Besides, the insignificant ones of the earth are not the least rich in talent, in an originality of invention which will teach us much concerning the infinite variety of instinct. The Cicadella, in particular, possesses her recipes for aerated waters. Let us ask her by what process she succeeds in giving such a fine head of froth to her product, for the books that talk about boiling cauldrons and Cuckoo-spit are silent on this subject, the only one worthy of narration.

The foamy mass has no very definite shape and is hardly larger than a hazel-nut. It is [429]remarkably persistent even when the insect is not working at it any longer. Deprived of its manufacturer, who would not fail to keep it going, and placed on a watch-glass, it lasts for more than twenty-four hours without evaporating or losing its bubbles. This persistency is striking, compared with the rapidity with which soapsuds, for instance, disappear.

Prolonged duration of the foam is necessary to the Cicadella, who would exhaust herself in the constant renewal of her products if her work were ordinary froth. Once the effervescent covering is obtained, it is essential that the insect should rest for a time, with no other task than to drink its fill and grow. And so the moisture converted into froth possesses a certain stickiness, conducive to longevity. It is slightly oily and trickles under one’s finger like a weak solution of gum.

The bubbles are small and even, being all of the same dimensions. You can see that they have been scrupulously gauged, one by one; you suspect the presence of a graduated tube. Like our chemists and druggists, the insect must have its drop-measures.

A single Cicadella is usually crouching invisible [430]in the depths of the foam; sometimes there are two or three or more. In such cases, it is a fortuitous association, the fabrics of the several workers being so close together that they merge into one common edifice.

Let us see the work begin and, with the aid of a magnifying-glass, follow the creature’s proceedings. With her sucker inserted up to the hilt and her six short legs firmly fixed, the Cicadella remains motionless, flat on her stomach on the long-suffering leaf. You expect to see froth issuing from the edge of the well, effervescing under the action of the insect’s implement, whose lancets, ascending and descending in turns and rubbing against each other like those of the Cicada, ought to make the sap foam as it is forced out. The froth, so it would seem, must come ready-made from the puncture. That is what the current descriptions of the Cicadella tell us; that was how I myself pictured it on the authority of the writers. All this is a huge mistake: the real thing is much more ingenious. It is a very clear liquid that comes up from the well, with no more trace of foam than in a dew-drop. Even so the Cicada, who possesses [431]similar tools, makes the spot at which she slakes her thirst give forth a limpid fluid, with not a vestige of froth to it. Therefore, notwithstanding its dexterity in sucking up liquids, the Cicadella’s mouth-apparatus has nothing to do with the manufacture of the foamy mattress. It supplies the raw material; another implement works it up. What implement? Have patience and we shall see.

The clear liquid rises imperceptibly and glides under the insect, which at last is half inundated. The work begins again without delay. To make white of egg into a froth we have two methods: we can whip it, thus dividing the sticky fluid into thin flakes and causing it to take in air in a network of cells; or we can blow into it and so inject air-bubbles right into the mass. Of these two methods, the Cicadella employs the second, which is less violent and more elegant. She blows her froth.

But how is the blowing done? The insect seems incapable of it, being devoid of any air-mechanism similar to that of the lungs. To breathe with tracheæ and to blow like a bellows are incompatible actions.

Agreed; but be sure that, if the insect [432]needs a blast of air for its manufactures, the blowing-machine will be there, most ingeniously contrived. This machine the Cicadella possesses at the tip of her abdomen, at the end of the intestine. Here, split lengthwise in the shape of a Y, a little pocket opens and shuts in turns, a pocket whose two lips close hermetically when joined.

Having said this, let us watch the performance. The insect lifts the tip of its abdomen out of the bath in which it is swimming. The pocket opens, sucks in the air of the atmosphere till it is full, then closes and dives down, the richer by its prize. Inside the liquid, the apparatus contracts. The captive air escapes as from a nozzle and produces a first bubble of froth. Forthwith the air-pocket returns to the upper air, opens, takes in a fresh load and goes down again closed, to immerse itself once more and blow in its gas. A new bubble is produced.

And so it goes on with chronometrical regularity, from second to second, the blowing-machine swinging upwards to open its valve and fill itself with air, downwards to dive into the liquid and send out its gaseous contents. Such is the air-measurer, the drop-glass [433]which accounts for the evenness of the frothy bubbles.

Ulysses, the favourite of the gods, received from the storm-dispenser, Æolus, bags in which the winds were confined. The carelessness of his crew, who untied the bags to find out what they contained, let loose a tempest which destroyed the fleet. I have seen those mythological wind-filled bags; I saw them years ago, when I was a child.

A peripatetic tinker, a son of Calabria, had set up between two stones the crucible in which a tin soup-tureen and plates were to be remelted. Æolus did the blowing, Æolus in the person of a little dark-skinned boy who, squatting on his heels, forced air towards the forge by alternately squeezing two goatskin bags, one on the right and one on the left. Thus must the prehistoric bronze-smelters have performed their task, they whose workshops and whose remains of copper-slag I find on the hills near my home: the blast of their furnaces was produced by these inflated skins.

The machine employed by my Æolus is pathetically simple. The hide of a goat, with the hair left on, is practically all that is necessary. It is a bag fastened at the [434]bottom over a nozzle, open at the top and supplied, by way of lips, with two little boards which, when brought together, close up the whole apparatus. These two stiff lips are each furnished with a leather handle, one for the thumb, the other for the four remaining fingers. The hand opens; the lips of the bag part and it fills with air. The hand closes and brings the boards together; the air imprisoned in the compressed bag escapes by the nozzle. The alternate working of the two bags gives a continuous blast.

Apart from continuity, which is not a favourable condition when the gas has to be discharged in small bubbles, the Cicadella’s bellows works like the Calabrian tinker’s. It is a flexible pocket with stiff lips, which alternately part and unite, opening to let the air enter and closing to keep it imprisoned. The contraction of the sides takes the place of the shrinking of the bag and puffs out the gaseous contents when the pocket is immersed.

He certainly had a lucky inspiration who first thought of confining the wind in a bag, as mythology tells us that Æolus did. The goatskin turned into a bellows gave us our metals, the essential matter whereof our [435]tools are made. Well, in this art of expelling air, an enormous source of progress, the Cicadella was the pioneer. She was blowing her froth before Tubalcain thought of urging the fire of his forge with a leather pouch. She was the first to invent bellows.

When, bubble by bubble, the foamy wrapper covers the insect to a height which the uplifted tip of her belly is unable to reach, it is no longer possible to take in air and the effervescence stops. Nevertheless, the gimlet that extracts the sap goes on working, for nourishment must be obtained. As a rule then, in the sloping part, the superfluous liquid, that which is not converted into foam, collects and forms a drop of perfectly clear liquid.

What does this limpid fluid lack in order to turn white and effervesce? Nothing but air blown into it, one would think. I am able to substitute my own devices for the Cicadella’s syringe. I place between my lips a very slender glass tube and with delicate puffs send my breath into the drop of moisture. To my great surprise, it does not froth up. The result is just the same as that which I should have with plain water from the tap.[436]

Instead of a plentiful, lasting, slow-subsiding foam, like that with which the insect covers itself, all that I obtain is a miserable ring of bubbles, which burst as soon as they appear. And I am equally unsuccessful with the liquid which the Cicadella collects under her abdomen at the start, before working her bellows. What is wrong in each case? The foamy product and its generating liquid shall tell us.

The first is oily to the touch, gummy and as fluid as, for instance, a weak solution of albumen would be; the second flows as readily as plain water. The Cicadella therefore does not draw from her well a liquid liable to effervesce merely by the action of the blow-pocket; she adds something to what oozes from the puncture, adds a viscous element which gives cohesion and makes frothing possible, even as a boy adds soap to the water which he blows into iridescent bubbles through a straw.

Where then does the insect keep its soap-works, its manufactory of the effervescent element? Evidently in the blow-pocket itself. It is here that the intestine ends and here that albuminous products, furnished either by the digestive canal or by special glands, [437]can be expelled in infinitesimal doses. Each whiff sent out is thus accompanied by a trifle of adhesive matter, which dissolves in the water, making it sticky and enabling it to retain the captive air in permanent bubbles. The Cicadella covers herself with an icing of which her intestine is to some extent the manufacturer.

This method brings us back to the industry of the lily-dweller, the grub which makes itself a loathsome armour out of its excretions;2 but what a distance between the heap of ordure which it wears on its back and the Cicadella’s aerated mattress!

Another fact, more difficult to explain, attracts our attention. A multitude of low-growing, herbaceous plants, whose sap starts flowing in April, suit the frothy insect, without distinction of species, genus or family. I could almost make a list of the non-ligneous vegetation of my neighbourhood by cataloguing the plants on which the little creature’s foam is to be found in greater or lesser abundance. A few experiments will tell us how indifferent the Cicadella is to both [438]the nature and the properties of the plant which she adopts as her home.

I pick the insect out of its froth with the tip of a hair-pencil and place it on some other plant, of an opposite flavour, letting the strong come after the mild, the spicy after the insipid, the bitter after the sweet. The new encampment is accepted without hesitation and soon covered with foam. For instance, a Cicadella taken from the bean, which has a neutral flavour, thrives excellently on the spurges, full of pungent milky sap, and particularly on Euphorbia serrata, the narrow notch-leaved spurge, which is one of her favourite dwelling-places. And she is equally satisfied when moved from the highly-spiced spurge to the comparatively flavourless bean.

This indifference is surprising when we reflect how scrupulously faithful other insects are to their plants. There are undoubtedly stomachs expressly made to drink corrosive and assimilate toxic matters. The caterpillar of Acherontia atropos, the Death’s-head Hawk-moth, eats its fill of potato-leaves, which are seasoned with solanin; the caterpillar of the Spurge-moth browses in these parts on the upright red spurge (Euphorbia [439]characias), whose milk produces much the same effect as red-hot iron on the tongue; but neither one nor the other would pass from these narcotics or these caustics to utterly insipid fare.

How does the Cicadella manage to feed on anything and everything, for she evidently obtains nourishment while putting a head on her liquid? I see her thrive, either of her own accord or by my devices, on the common buttercup (Ranunculus acris), which has a flavour unequalled save by Cayenne pepper; on the Italian arum (Arum italicum), the veriest particle of whose leaves is enough to burn the lips; on the traveller’s joy, or virgin’s bower (Clematis vitalba), the famous beggars’ herb, which reddens the skin and produces the sores in request among our sham cripples. After these highly-seasoned condiments, she will promptly accept the mild sainfoin, the scented savory, the bitter dandelion, the sweet field eringo, in short, anything that I put before her, whether full-flavoured or tasteless.

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 [440]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? [441]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 [442]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.

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.[443]

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: [444]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.

The Cicadella is better-advised and altogether escapes the dangers attendant on a removal. Subject to certain summary changes which never interrupt her activity, she assumes the adult form in the very heart of her bastion, under the shelter of a viscous rampart capable of repelling any assailant. Here she enjoys perfect security when the difficult hour has come for tearing off her old skin and putting on another, brand-new and more decorative; here she finds profound peace for her excoriation and for the display of the attire of a riper age.

The insect does not leave its cool covering until it is grown up, when it appears in [445]the form of a pretty little, brown-striped Cicadella. It is then able to take enormous and sudden leaps, which carry it far from the aggressor; and it leads an easy life, untroubled by the foe.

Looked upon as a system of defence, the frothy stronghold is indeed a magnificent invention, much superior to the squalid work of the invader of the lily. And, strange to say, the system has no imitators among the genera most nearly allied to the froth-blower.

In her larval form, the Asparagus-beetle is victimized by the Fly because she does not follow the example of her cousin, the Lily-beetle, and clothe herself in her own droppings. Even so, on the grass, on the trees displaying their tender leaves, other Cicadellæ abound, no less exposed to danger from the Warbler seeking a succulent morsel for his little ones; and, as they draw out the sap through the punctures made by their suckers, not one of them thinks of making it effervesce. Yet they too possess the elevator-pump, which they all work in the same manner; only they do not know how to turn the end of their intestine into a bellows. Why not? Because instincts are not to be [446]acquired. They are primordial aptitudes, bestowed here and denied there; time cannot awaken them by a slow incubation, nor are they decreed by any similarity of organization.