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 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 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 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 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.
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 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, 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 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 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 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. [82] 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 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 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 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 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 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. [83]
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. [84]
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 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 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.
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 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 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 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.