THE LOCUSTS: THEIR EGGS

What can our Locusts do? Not much in the way of manufactures. Their business in the world is that of alchemists who in their gourdlike stomach elaborate and refine material destined for higher objects. As I sit by my fireside, in the evening hours of meditation, scribbling these notes upon the part which Locusts play in life, I am not prepared to say that they have not contributed from time to time to the awakening of thought, that magic mirror of things. They are on the earth to thrive as best they can and to multiply, the latter being the highest law of animals charged with the manufacture of foodstuffs.

From the former point of view, if we except the all-devouring tribes which at times imperil the very existence of Africa, the Locusts hardly attract our attention. They are poor trenchermen; and I can surfeit a whole [379]barrack-room in my cages with a leaf of lettuce. As for the way in which they multiply, that is another matter and one well worth a moment’s attention.

At the same time we must not look for the nuptial eccentricities of the Grasshoppers. Despite close similarity of structure, we are here in a new world as regards habits and character. In the peaceful Locust clan, all that has to do with pairing is correct, free from impropriety and conducted in accordance with the customary rites of the entomological world. Any one keeping it under observation at the time of the procreative frenzy will realize that the Locust came later than the Grasshopper, after the primitive Orthopteron had sown his monstrous wild oats. There is nothing striking to be said therefore on this always delicate subject; and I am very glad of it. Let us pass on and come to the eggs.

At the end of August, a little before noon-day, let us keep a close watch on the Italian Locust (Caloptenus italicus, Lin.), the boldest hopper of my neighbourhood. He is a sturdy fellow, very free with his kicks; and he is clad in short wing-cases that hardly reach the tip of his abdomen. His costume [380]is usually russet, with brown patches. A few more elegant ones edge the corselet with a whitish hem which is prolonged over the head and wing-cases. The wings are colourless except at the base, where they are pink; the hinder shins are claret-coloured.

The mother selects a suitable spot for her eggs on the side where the sun is hottest and always at the edge of the cage, whose wirework supplies her with a support in case of need. Slowly and laboriously she drives her clumsy drill perpendicularly into the sand, this drill being her abdomen, which disappears entirely. In the absence of proper boring-tools, the descent underground is painful and hesitating, but is at last accomplished thanks to perseverance, that powerful lever of the weak.

The mother is now installed, half-buried in the soil. She gives slight starts, which follow one another at regular intervals and seem to correspond with the efforts of the oviduct as it expels the eggs. The neck gives throbs that lift and lower the head with slight jerks. Apart from these pulsations of the head, the body, in its only visible half, the fore-part, is absolutely stationary, so intense is the creature’s absorption in her [381]laying. It is not unusual for a male, by comparison a dwarf, to come near and for a long time to gaze curiously at the travailing mother. Sometimes also a few females stand around, with their big faces turned towards their friend in labour. They seem to take an interest in what is happening, perhaps saying to themselves that it will be their turn soon.

After some forty minutes of immobility, the mother suddenly releases herself and bounds far away. She gives not a look at the eggs nor a touch of the broom to conceal the aperture of the well. The hole closes of its own accord, as best it can, by the natural falling-in of the sand. It is an extremely summary performance, marked by an utter absence of maternal solicitude. The Locust mother is not a model of affection.

Others do not forsake their eggs so recklessly. I can name the ordinary Locust with the blue wings striped with black (Œdipoda cœrulescens, Lin.); also Pachytylus nigrofasciatus, De Geer, whose cognomen lacks point, for it ought to suggest either the malachite-green patches of the costume or the white cross of the corselet.

Both, when laying their eggs, adopt the [382]same attitude as the Italian Locust. The abdomen is driven perpendicularly into the soil; the rest of the body partly disappears under the sliding sand. We again see a long period of immobility, exceeding half an hour, together with little jerks of the head, a sign of the underground efforts.

The two mothers at last release themselves. With their hind-legs, lifted on high, they sweep a little sand over the orifice of the pit and press it down by stamping rapidly. It is a pretty sight to watch the precipitous action of their slender legs, blue or pink, giving alternate kicks to the opening which is waiting to be plugged. In this manner, with a lively trampling, the entrance to the house is closed and hidden away. The hole in which the eggs were laid disappears from sight, so well obliterated that no evil-intentioned creature could hope to discover it by means of vision alone.

Nor is this all. The driving-power of the two rammers is the hinder thighs, which, in rising and falling, scrape lightly against the edge of the wing-cases. This bow-play produces a faint stridulation, similar to that with which the insect placidly lulls itself to sleep in the sun.[383]

The Hen salutes the egg which she has just laid with a song of gladness; she announces her maternal joys, to the whole neighbourhood. Even so does the Locust do in many cases. With her thin scraper, she celebrates the advent of her family. She says:

“Non omnis moriar; I have buried underground the treasure of the future; I have entrusted to the incubation of the great hatcher a keg of germs which will take my place.”

Everything on the site of the nest is put right in one brief spell of work. The mother then leaves the spot, refreshes herself after her exertions with a few mouthfuls of green stuff and prepares to begin again.

The largest of the Acridians in our part of the country, the Grey Locust (Pachytylus cinerescens, Fabr.), rivals the African Locusts in size, without possessing their calamitous habits. He is peace-loving and temperate and above reproach where the fruits of the earth are concerned. From him we obtain a little information which is easily verified by observing the insect in captivity.

The eggs are laid about the end of April, a few days after the pairing, which lasts [384]some little while. The female is armed at the tip of the abdomen—as, in varying degrees, are the other Locust mothers—with four short excavators, arranged in pairs and shaped like a hooked finger-nail. In the upper pair, which are larger, these hooks are turned upwards; in the lower and smaller pair, they are turned downwards. They form a sort of claw and are hard and black at the point; also they are scooped out slightly, like a spoon, on their concave surface. These are the pick-axes, the trepans, the boring-tools.

The mother bends her long abdomen perpendicularly to the line of the body. With her four trepans she bites into the soil, lifting the dry earth a little; then, with a very slow movement, she pushes down her abdomen, making no apparent effort, displaying no excitement that would reveal the difficulty of the task.

The insect is motionless and contemplative. The boring-implement could not work more quietly if it were sinking into soft mould. It might all be happening in butter; and yet what the bore traverses is caked, unyielding earth.

It would be interesting, if it were only possible, [385]to see the perforating-tool, the four gimlets, at work. Unfortunately, things happen in the mysteries of the earth. No rubbish rises to the surface; nothing denotes the underground labour. Little by little the abdomen sinks softly in, as our finger would sink into a lump of soft clay. The four trepans must open the passage, crumbling the earth into dust which is thrust back sideways by the abdomen and packed as with a gardener’s dibble.

The best site for laying the eggs is not always found at the first endeavour. I have seen the mother drive her abdomen right in and make five wells one after the other before finding a suitable place. The pits recognized as defective are abandoned as soon as bored. They are vertical, cylindrical holes, of the diameter of a thick lead-pencil and astonishingly neat. No wimble would produce cleaner work. Their length is that of the insect’s abdomen, distended as far as the extension of the segments allows.

At the sixth attempt, the spot is recognized as propitious. The laying thereupon takes place, but nothing outside betrays the fact, so motionless does the mother seem, with her abdomen immersed up to the hilt, which [386]causes the long wings lying on the ground to rumple and open out. The operation lasts for a good hour.

At last the abdomen rises, little by little. It is now near the surface, in a favourable position for observation. The valves are in continual movement, whipping a mucus which sets in milk-white foam. It is very similar to the work done by the Mantis when enveloping her eggs in froth.

The foamy matter forms a nipple at the entrance to the well, a knob which stands well up and attracts the eye by the whiteness of its colour against the grey background of the soil. It is soft and sticky, but hardens pretty soon. When this closing button is finished, the mother moves away and troubles no more about her eggs, of which she lays a fresh batch elsewhere after a few days have intervened.

At other times, the terminal foamy paste does not reach the surface; it stops some way down and, before long, is covered with the sand that slips from the margin. There is then nothing outside to mark the place where the eggs were laid.

Even when they concealed the mouth of the well under a layer of swept sand, my [387]various captives, large and small, were too assiduously watched by me to foil my curiosity. I know in every case the exact spot where the barrel of eggs lies. The time has come to inspect it.

The thing is easily discovered, an inch or an inch and a half down, with the point of a knife. Its shape varies a good deal in the different species, but the fundamental structure remains the same. It is always a sheath made of solidified foam, a similar foam to that of the nests of the Praying Mantis. Grains of sand stuck together give it a rough outer covering.

The mother has not actually made this coarse cover, which constitutes a defensive wall. The mineral wrapper results from the simple infiltration of the product, at first semifluid and viscous, that accompanies the emission of the eggs. The wall of the pocket absorbs it and, swiftly hardening, becomes a cemented scabbard, without the agency of any special labour on the insect’s part.

Inside, there is no foreign matter, nothing but foam and eggs. The latter occupy only the lower portion, where they are immersed in a frothy matrix and packed one on top [388]of the other, slantwise. The upper portion, which is larger in some cases than in others, consists solely of soft, yielding foam. Because of the part which it plays when the young larvæ come into existence, I shall call it the ascending-shaft. A final point worthy of observation is that all the sheaths are planted more or less vertically in the soil and end at the top almost level with the ground.

We will now describe specifically the layings which we find in the cages. That of Pachytylus cinerescens is a cylinder six centimetres long and eight millimetres wide.1 The upper end, when it emerges above the ground, swells into a nipple. All the rest is of uniform thickness. The yellow-grey eggs are fusiform. Immersed in the froth and arranged slantwise, they occupy only about a sixth part of the total length. The rest of the structure is a fine, white, very powdery foam, soiled on the outside by grains of earth. The eggs are not many in number, about thirty; but the mother lays several batches.

That of P. nigrofasciatus is shaped like a slightly curved cylinder, rounded off at the [389]lower end and cut square at the upper end. Its dimensions are an inch to an inch and a half in length by a fifth of an inch in width. The eggs, about twenty in number, are orange-red, adorned with a pretty pattern of tiny spots. The frothy matrix in which they are contained is small in quantity; but above them there is a long column of very fine, transparent and porous foam.

The Blue-winged Locust (Œdipoda cærulescens) arranges her eggs in a sort of fat inverted comma. The lower portion contains the eggs in its gourd-shaped pocket. They also are few in number, some thirty at most, of a fairly bright orange-red, but unspotted. This receptable is crowned with a curved, conical cap of foam.

The lover of the mountain-tops, the Pedestrian Locust, adopts the same method as the Blue-winged Locust, the denizen of the plains. Her sheath too is shaped like a comma with the point turned upwards. The eggs, numbering about two dozen, are dark-russet and are strikingly ornamented with a delicate lacework of inwrought spots. You are quite surprised when you pass the magnifying-glass over this unexpected elegance. Beauty leaves its impress everywhere, even [390]in the humble covering of an unsightly Acridian incapable of flight.

The Italian Locust begins by enclosing her eggs in a keg and then, when on the point of sealing her receptacle, thinks better of it: something essential, the ascending-shaft, is lacking. At the upper end, at the point where it seems as if the barrel ought to finish and close, a sudden compression changes the course of the work, which is prolonged by the regulation foamy appendage. In this way, two storeys are obtained, clearly defined on the outside by a deep groove. The lower, which is oval in shape, contains the packet of eggs; the upper, tapering into the tail of a comma, consists of nothing but foam. The two communicate by an opening that remains more or less free.

The Locust’s art is not confined to these specimens of architecture. She knows how to construct other strong-boxes for her eggs; she can protect them with all kinds of edifices, some simple, others more ingenious, but all worthy of our attention. Those with which we are familiar are very few compared with those of which we are ignorant. No matter: what the cages reveal to us is sufficient to enlighten us as to the general form. It remains [391]for us to learn how the building—an egg-warehouse below, a foamy turret above—is constructed.

Direct observation is impracticable here. If we took it into our heads to dig and to uncover the abdomen at work, the mother, worried by our importunity, would leap away without telling us anything. Fortunately, one Locust, the strangest of my district, reveals the secret to us. I speak of the Tryxalis, the largest member of the family, after the Grey Locust.

Though inferior to the last-named in size, how far she exceeds her in slenderness of figure and, above all, in originality of shape! On our sun-scorched swards, none has a leaping-apparatus to compare with hers. What hind-legs, what extravagant thighs, what shanks! They are longer than the creature’s whole body.

The result obtained hardly corresponds with this extraordinary length of limb. The insect shuffles awkwardly along the edges of the vines, on the sand sparsely covered with grass; it seems embarrassed by its shanks, which are slow to work. With this equipment, weakened by its excessive length, the leap is awkward, describing but a short [392]parabola. The flight alone, once taken, is of a certain range, thanks to an excellent pair of wings.

And then what a strange head! It is an elongated cone, a sugar-loaf, whose point, turned up in the air, has earned for the insect the quaint epithet of nasuta, long-nosed. At the top of this cranial promontory are two large, gleaming, oval eyes and two antennæ, flat and pointed, like dagger-blades. These rapiers are organs of information. The Tryxalis lowers them, with a sudden swoop, to explore with their points the object in which she is interested, the bit which she intends to nibble.

To this abnormal shape we must add another characteristic that makes this long-shanks an exception among Acridians. The ordinary Locusts, a peaceful tribe, live among themselves without strife, even when driven by hunger. The Tryxalis, on the other hand, is somewhat addicted to the cannibalism of the Grasshoppers. In my cages, in the midst of plenty, she varies her diet and passes easily from salad to game. When tired of green stuff, she does not scruple to exercise her jaws on her weaker companions.

This is the creature capable of giving us [393]information about methods of laying. In my cages, as the result of an aberration due no doubt to the boredom of captivity, it has never laid its eggs in the ground. I have always seen it operating in the open air and even perched on high.2 In the early days of October, the insect clings to the trelliswork of the cage and very slowly discharges its batch of eggs, which we see gushing forth in a fine, foamy stream, soon stiffening into a thick cylindrical cord, knotty and queerly curved. It takes nearly an hour to complete the emission. Then the thing falls to the ground, no matter where, unheeded by the mother, who never troubles about it again.

The shapeless object, which varies greatly in different layings, is at first straw-coloured, then darkens and turns rusty-brown on the morrow. The fore-part, which is the first ejected, usually consists only of foam; the hinder part alone is fertile and contains the eggs, buried in a frothy matrix. They are amber-yellow, about a score in number and shaped like blunt spindles, eight to nine millimetres in length.3[394]

The sterile end, which is at least as big as the other, tells us that the apparatus which produces the foam is in operation before the oviduct and afterwards goes on while the latter is working.

By what mechanism does the Tryxalis froth up her viscous product into a porous column first and a mattress for the eggs afterwards? She must certainly know the method of the Praying Mantis, who, with the aid of spoon-shaped valves, whips and beats her glair and converts it into an omelette soufflée; but in the Acridian’s case the frothing is done within and there is nothing outside to betray its existence. The glue is foamy from the moment of its appearing in the open air.

In the Mantis’ building, that complex work of art, it is not a case of any special talent, which the mother can exercise at will. The wonderful egg-casket comes from the ordinary action of the mechanism, is merely the outcome of the organization. A fortiori, the Tryxalis, in discharging her clumsy sausage, is purely a machine. The thing happens of itself.

The same applies to the Locusts. They have no industry of their own specially devised [395]for laying eggs in strata in a keg of froth and extending this keg into an ascending-shaft. The mother, with her abdomen plunged into the sand, expels at the same time eggs and foamy glair. The whole becomes coordinated of its own accord simply by the mechanism of the organs: on the outside, the frothy material, which coagulates and becomes encrusted with a bulwark of earth; in the centre and at the bottom, the eggs arranged in regular strata; at the upper end, a column of yielding foam.

The Tryxalis and the Grey Locust are early hatchers. The latter’s family are already hopping on the yellow patches of grass in August; before October is out, we are frequently coming across young larvæ with pointed skulls. But in most of the other Acridians the ovigerous sheaths last through the winter and do not open until the fine weather returns. They are buried at no great depth in a soil which is at first loose and dusty and which would not be likely to interfere with the emergence of the young larvæ if it remained as it is; but the winter rains cake it together and turn it into a hard ceiling. Suppose that the hatching takes place only a couple of inches down: how is [396]this crust to be broken, how is the larva to come up from below? The mother’s unconscious art has provided for that.

The Locust at his birth finds above him, not rough sand and hardened earth, but a perpendicular tunnel whose solid walls keep all difficulties at a distance, a road protected by a little easily-penetrated foam, an ascending-shaft, in short, which brings the new-born larva quite close to the surface. Here a finger’s-breadth of serious obstacle remains to be overcome.

The greater part of the emergence therefore is accomplished without effort, thanks to the terminal appendage of the egg-barrel. If, in my desire to follow the underground work of the exodus, I experiment in glass tubes, almost all the new-born larvæ die, exhausted with fatigue, under an inch of earth, when I do away with the liberating appendage to the shells. They duly come to light if I leave the nest in its integral condition, with the ascending-shaft pointing upwards. Though a mechanical product of the organism, created without any effort of the creature’s intelligence, the Locust’s edifice, we must confess, is singularly well thought out.[397]

Having come quite close to the surface with the aid of his ascending-shaft, what does the young Locust do to complete his deliverance? He has still to pass through a layer of earth about a finger’s-breadth in thickness; and that is very hard work for budding flesh.

If we keep the egg-cases in glass tubes during the favourable period, the end of spring, we shall receive a reply to our question, provided that we have the requisite patience. The Blue-winged Locusts lend themselves best to my investigations. I find some of them busied with the work of liberation at the end of June.

The little Locust, on leaving his shell, is a whitish colour, clouded with light red. His progress is made by wormlike movements; and, so that it may be impeded as little as possible, he is hatched in the condition of a mummy, that is to say, clad, like the young Grasshoppers, in a temporary jacket, which keeps his antennæ, palpi and legs closely fixed to his breast and belly. The head itself is very much bent. The large hind-thighs are arranged side by side with the folded shanks, shapeless as yet, short and as it were crooked. On the way, the [398]legs are slightly released; the hind-legs are straightened out and afford a fulcrum for the sapping-work.

The boring-tool, a repetition of the Grasshoppers’, is at the neck. There is here a tumour that swells, subsides, throbs and strikes the obstacle with pistonlike regularity. A tiny and most tender cervical bladder engages in a struggle with quartz. At the sight of this capsule of glair striving to overcome the hardness of the mineral, I am seized with pity. I come to the unhappy creature’s assistance by slightly damping the layer to be passed through.

Despite my intervention, the task is so arduous that, in an hour, I see the indefatigable one make a progress of hardly a twenty-fifth of an inch. How you must labour, you poor little thing, how you must persevere with your throbbing head and writhing loins, before you can clear a passage for yourself through the thin layer which my kindly drop of water has softened for you!

The ineffectual efforts of the tiny mite tell us plainly that the emergence into the light of day is an enormous undertaking, in which, but for the aid of the exit-tunnel, the [399]mother’s work, the greater number would succumb.

It is true that the Grasshoppers, similarly equipped, find it even more difficult to make their way out of the earth. Their eggs are laid naked in the ground; no outward passage is prepared for them beforehand. We may assume, therefore, that the mortality must be very high among these improvident ones; legions are bound to perish at the time of the exodus.

This is confirmed by the comparative scarcity of Grasshoppers and the extreme abundance of Locusts. And yet the number of eggs laid is about the same in both cases. The Locust does not, in fact, limit herself to a single casket containing a score of eggs: she puts into the ground two, three and more, which gives a total population approaching that of the Decticus and other Grasshoppers. If, to the greater delight of the consumers of small game, she thrives so well, whereas the Grasshopper, who is quite as fertile but less ingenious, dwindles, does she not owe it to that superb invention, her exit-turret?

One last word upon the tiny insect which, for days on end, fights away with its cervical [400]rammer. It is outside at last and rests for a moment, to recover from all that fatigue. Then, suddenly, under the thrust of the throbbing blister, the temporary jacket splits. The rags are pushed back by the hind-legs, which are the last to strip. The thing is done: the creature is free, pale in colouring as yet, but possessing the final larval form.

Then and there, the hind-legs, hitherto stretched in a straight line, adopt the regulation position; the legs fold under the great thighs; and the spring is ready to work. It works. Little Locust makes his entrance into the world and hops for the first time. I offer him a bit of lettuce the size of my finger-nail. He refuses. Before taking nourishment, he must first mature and develop for a while in the sun.