THE WHITE-FACED DECTICUS: THE LAYING AND THE HATCHING OF THE EGGS
The White-faced Decticus is an African insect that in France hardly
ventures beyond the borders of Provence and Languedoc. She wants the
sun that ripens the olives. Can it be that a high temperature acts as a
stimulus to her matrimonial eccentricities, or are we to look upon
these as family customs, independent of climate? Do things happen under
frosty skies just as they do under a burning sun?
I go for my information to another Decticus, the Alpine Analota (A.
alpina, Yersin), who inhabits the high ridges of Mont Ventoux, [48]
which are covered with snow for half the year. Many a time, during my
old botanical expeditions, I had noticed the portly insect hopping
among the stones from one bit of turf to the next. This time, I do not
go in search of it: it reaches me by post. Following my indications, an
obliging forester [49] climbs up there twice in the first fortnight of
August and brings me back the wherewithal to fill a cage comfortably.
In shape and colouring it is a curious specimen of the Grasshopper
family. Satin-white underneath, it has the upper part sometimes
olive-black, sometimes bright-green or pale-brown. The organs of flight
are reduced to mere vestiges. The female has as wing-cases two short
white scales, some distance apart; the male shelters under the edge of
his corselet two little concave plates, also white, but laid one on top
of the other, the left on the right.
These two tiny cupolas, with bow and sounding-board, rather suggest, on
a smaller scale, the musical instrument of the Ephippiger, whom the
mountain insect resembles to some extent in general appearance.
I do not know what sort of tune cymbals so small as these can produce.
I do not remember ever hearing them in their native haunts; and three
months’ home breeding gives me no further information in this respect.
Though they lead a joyous life, my captives are always dumb.
The exiles do not seem greatly to regret their cold peaks, among the
orange poppies and saxifrages of arctic climes. What used they to
browse upon up there? The Alpine meadow-grass, Mont-Cenis violets,
Allioni’s bell-flower? I do not know. In the absence of Alpine grasses,
I give them the common endive from my garden. They accept it without
hesitation.
They also accept such Locusts as can offer only a feeble resistance;
and the diet alternates between animal and vegetable fare. They even
practise cannibalism. If one of my Alpine visitors limps and drags a
leg, the others eat him up. So far I have seen nothing striking: these
are the usual Grasshopper manners.
The interesting sight is the pairing, which occurs suddenly, without
any prelude. The meeting takes place sometimes on the ground, sometimes
on the wirework of the cage. In the latter case, the sword-bearer,
firmly hooked to the trellis, supports the whole weight of the couple.
The other is back downwards, his head pointing to his mate’s tail. With
his long, fleshy-shanked hind-legs, he gets a grip of her sides; with
his four front legs, often also with his mandibles, he grasps and
squeezes the sabre, which projects slantwise. Thus hanging to this sort
of greased pole, he operates in space.
When the meeting takes place on the ground, the couple occupy the same
position, only the male is lying on his back in the sand. In both cases
the result is an opal grain which, in the visible part of it, resembles
in shape and size the swollen end of a grape-pip.
As soon as this object is in position, the male decamps at full speed.
Can he be in danger? Possibly, to judge from what I have seen. I admit
that I have seen it only once.
The bride in this case was grappling with two rivals. One of them,
hanging to the sabre, was at work in due form behind; the other, in
front, tightly clawed and with his belly ripped open, was waving his
limbs in vain protest against the harpy crunching him impassively in
small mouthfuls. I had before my eyes, under even more atrocious
conditions, the horrors which the Praying Mantis had shown me in the
old days: unbridled rut; carnage and voluptuousness in one; a
reminiscence perhaps of ancient savagery.
As a rule, the male, a dwarf by comparison with the female, hastens to
run away as soon as his task is consummated. The deserted one makes no
movement. Then, after waiting twenty minutes or so, she curves herself
into a ring and proceeds to enjoy the final banquet. She pulls the
sticky raisin-pip into shreds which are chewed with grave appreciation
and then gulped down. It takes her more than an hour to swallow the
thing. When not a crumb remains, she descends from the wire gauze and
mingles with the herd. Her eggs will be laid in a day or two.
The proof is established. The matrimonial habits of the White-faced
Decticus are not an exception due to the heat of the climate: the
Grasshopper from the cold peaks shares them and surpasses them.
We will return to the big Decticus with the ivory face. The laying
follows close upon the strange events which we have described. It is
done piecemeal, as the ovaries ripen. Firmly planted on her six legs,
the mother bends her abdomen into a semicircle and drives her sabre
perpendicularly into the soil, which, consisting in my cages of sifted
earth, presents no serious resistance. The ovipositor therefore
descends without hesitation and enters up to the hilt, that is to say,
to a depth of about an inch.
For nearly fifteen minutes, absolute immobility. This is the time when
the eggs are being laid. At last the sabre comes up a little way and
the abdomen swings briskly from side to side, communicating an
alternate transversal movement to the implement. This tends to scrape
out and widen the sunken hole; it also has the effect of releasing from
the walls earthy materials which fill up the bottom of the cavity.
Thereupon the ovipositor, which is half in and half out, rams down this
dust. It comes up a short distance and then dips repeatedly, with a
sudden, jerky movement. We should work in the same way with a stick to
ram down the earth in a perpendicular hole. Thus alternating the
transversal swing of the sabre with the blows of the rammer, the mother
covers up the well pretty quickly.
The external traces of the work have still to be done away with. The
insect’s legs, which I expected to see brought into play, remain
inactive and keep the position adopted for laying the eggs. The sabre
alone scratches, sweeps and smooths the ground with its point, very
clumsily, it must be admitted.
Now all is in order. The abdomen and the ovipositor are restored to
their normal positions. The mother allows herself a moment’s rest and
goes to take a turn in the neighbourhood. Soon she comes back to the
site where she has already laid her eggs and, very near the original
spot, which she recognizes clearly, she drives in her tool afresh. The
same proceedings as before are repeated.
Follow another rest, another exploration of the vicinity, another
return to the place already sown. For the third time the pointed stake
descends, only a very slight distance away from the previous hole.
During the brief hour that I am watching her, I see her resume her
laying five times, after breaking off to take a little stroll in the
neighbourhood; and the points selected are always very close together.
On the following days, at varying intervals, the sowing is renewed for
a certain number of times which I am not able to state exactly. In the
case of each of these partial layings, the site changes, now here, now
there, as this or that spot is deemed the more propitious.
When everything is finished, I examine the little pits in which the
Decticus placed her eggs. There are no packets in a foamy sheath, such
as the Locust supplies; no cells either. The eggs lie singly, without
any protection. I gather three score as the total product of one
mother. They are of a pale lilac-grey and are drawn out shuttlewise, in
a narrow ellipsoid five or six millimetres long. [50]
The same isolation marks those of the Grey Decticus, which are black;
those of the Vine Ephippiger, which are ashen-grey; and those of the
Alpine Analota, which are pale-lilac. The eggs of the Green
Grasshopper, which are a very dark olive-brown and, like those of the
White-faced Decticus, about sixty in number, are sometimes arranged
singly and sometimes stuck together in little clusters.
These different examples show us that the Grasshoppers plant with a
dibble. Instead of packing their seeds in little casks of hardened
foam, like the Locusts, they put them into the earth one by one or in
very small clusters.
The hatching is worth examination; I will explain why presently. I
therefore gather plenty of eggs of the big Decticus at the end of
August and place them in a small glass jar with a layer of sand.
Without undergoing any apparent modification, they spend eight months
here under cover, sheltered from the frosts, the showers and the
overpowering heat of the sun that would await them under natural
conditions.
When June comes, I often meet young Dectici in the fields. Some are
already half their adult size, which is evidence of an early appearance
dating back to the first fine days of the year. Nevertheless my jar
shows no signs of any imminent hatching. I find the eggs just as I
gathered them nine months ago, neither wrinkled nor tarnished, wearing,
on the contrary, a most healthy look. What causes this indefinitely
prolonged delay?
A suspicion occurs to me. The eggs of the Grasshopper tribe are planted
in the earth like seeds. They are there exposed, without any kind of
protection, to the watery influence of the snow and the rain. Those in
my jar have spent two-thirds of the year in a state of comparative
dryness. Perhaps, in order to hatch, they lack what grain absolutely
needs in order to sprout. Animal seeds as they are, they may yet
require under earth the moisture necessary to vegetable seeds. Let us
try.
I place at the bottom of some glass tubes, to enable me to make certain
observations which I have in mind, a pinch of backward eggs taken from
my collection; and on the top I heap lightly a layer of very fine, damp
sand. The receptacle is closed with a plug of wet cotton, which will
maintain a constant moisture in the interior. The column of sand
measures about an inch, which is very much the depth at which the
ovipositor places the eggs. Any one seeing my preparations and
unacquainted with their object would hardly suspect them of being
incubators; he would be more likely to think them the apparatus of a
botanist who was experimenting with seeds.
My anticipation was correct. Favoured by the high temperature of the
summer solstice, the Grasshopper seed does not take long to sprout. The
eggs swell; the front end of each is spotted with two dark dots, the
rudiments of the eyes. It is quite evident that the bursting of the
shell is near at hand.
I spend a fortnight in keeping a tedious watch at every hour of the
day: I have to surprise the young Decticus actually leaving the egg, if
I want to solve a question that has long been vexing my mind. The
question is this: the Grasshopper’s egg is buried at a varying depth,
according to the length of the ovipositor or dibble. An inch is about
the most for the seeds of the best-equipped insects in our parts. Now
the newborn Decticus, hopping awkwardly in the grass at the approach of
summer, is, like the adult, endowed with a pair of very long tentacles,
vying with hairs for slenderness; he carries behind him two
extraordinary legs, two enormous hinged levers, a pair of
jumping-stilts that would be very inconvenient for ordinary walking.
How does the feeble little creature set to work, with this cumbrous
luggage, to emerge from the earth? By what artifice does it manage to
clear a passage through the rough soil? With its antennary plumes,
which an atom of sand can break, with its immense shanks, which the
least effort is enough to disjoint, the mite is obviously incapable of
reaching the surface and freeing itself.
The miner going underground puts on a protective dress. The little
Grasshopper also, making a hole in the earth in the opposite direction,
must don an overall for emerging from the earth; he must possess a
simpler, more compact transition-form, which enables him to come out
through the sand, a delivery-shape analogous to that which the Cicada
and the Praying Mantis use at the moment of issuing, one from his twig,
the other from the labyrinth of his nest.
Reality and logic here agree. The Decticus, in point of fact, does not
leave the egg in the form in which I see him, the day after his birth,
hopping on the lawn; he possesses a temporary structure better-suited
to the difficulties of the emergence. Coloured a delicate flesh-white,
the tiny creature is cased in a scabbard which keeps the six legs
flattened against the abdomen, stretching backwards, inert. In order to
slip more easily under the ground, he has his shanks tied up beside his
body. The antennæ, those other irksome appendages, are motionless,
pressed against the parcel.
The head is very much bent against the chest. With its big, black
ocular specks and its undecided and rather bloated mask, it suggests a
diver’s helmet. The neck opens wide at the back and, with a slow
throbbing, by turns swells and subsides. That is the motor. The
new-born insect moves along with the aid of its occipital hernia. When
uninflated, the fore-part pushes back the damp sand a little way and
slips into it by digging a tiny pit; then, blown out, it becomes a
knob, which moulds itself and finds a support in the depression
obtained. Then the rear-end contracts; and this gives a step forward.
Each thrust of the locomotive blister means nearly a millimetre [51]
traversed.
It is pitiful to see this budding flesh, scarcely tinged with pink,
knocking with its dropsical neck and ramming the rough soil. The animal
glair, not yet quite hardened, struggles painfully with stone; and its
efforts are so well directed that, in the space of a morning, a gallery
opens, either straight or winding, an inch long and as wide as an
average straw. In this way the harassed insect reaches the surface.
Half-caught in its exit-shaft, the disinterred one halts, waits for its
strength to return and then for the last time swells its occipital
hernia as far as it will go and bursts the sheath that has protected it
so far. The creature throws off its miner’s overall.
Here at last is the Decticus in his youthful shape, quite pale still,
but darker the next day and a regular blackamoor compared with the
adult. As a prelude to the ivory face of a riper age, he sports a
narrow white stripe under his hinder thighs.
Little Decticus, hatched before my eyes, life opens for you very
harshly! Many of your kindred must die of exhaustion before attaining
their freedom. In my tubes I see numbers who, stopped by a grain of
sand, succumb half-way and become furred with a sort of silky mildew.
The mouldy part soon absorbs their poor little remains. When performed
without my assistance, the coming to the light of day must be attended
with even greater dangers. The usual soil is coarse and baked by the
sun. Without a fall of rain, how do they manage, these immured ones?
More fortunate in my tubes with their sifted and wetted mould, here you
are outside, you little white-striped nigger; you bite at the
lettuce-leaf which I have given you; you leap about gaily in the cage
where I have housed you. It would be easy to rear you, I can see, but
it would not give me much fresh information. Let us then part company.
I restore you to liberty. In return for what you have taught me, I
bestow upon you the grass and the Locusts in the garden.
Thanks to you, I know that Grasshoppers, in order to leave the ground
in which the eggs are laid, possess a provisional shape, a primary
larval stage, which keeps those too cumbrous parts, the long legs and
antennæ, swathed in a common sheath; I know that this sort of mummy,
fit only to lengthen and shorten itself a little, has for an organ of
locomotion a hernia in the neck, a throbbing blister, an original piece
of mechanism which I have never seen used elsewhere as an aid to
progression. [52]