THE GREAT CERCERIS
With my memory full of the prowess of the Buprestis-huntress, I watched
for an opportunity to observe in my turn the labours of the Cerceres;
and I watched to such good purpose that I ended by being successful.
True, the Wasp was not the one celebrated by Léon Dufour, with her
sumptuous victuals whose remains, when unearthed, suggest the dust of
some nugget broken by the gold-miner’s pick: it was a kindred species,
a gigantic brigand who contents herself with humbler prey; in short, it
was Cerceris tuberculata or C. major, the largest and most powerful of
the genus.
The last fortnight in September is the time when our Burrowing Wasp
digs her lairs and buries in their depths the victim destined for her
grubs. The site of the home, always selected with discrimination, is
subject to those mysterious laws which differ in different species but
are invariable throughout any one species. Léon Dufour’s Cerceris
requires a level, well-trodden, compact soil, such as that of a path,
to prevent the possibility of landslips and other damage which would
ruin her gallery at the first shower of rain. Ours, on the contrary, is
not very particular about the nature of her soil, but must have that
soil vertical. With this slight architectural modification, she avoids
most of the dangers that might threaten her gallery; and consequently
she digs her burrows indifferently in a loose and slightly clayey soil
and in the soft sand of the Molasse formation, which makes the work of
excavation much easier. The only indispensable condition appears to be
that the earth should be dry and exposed to the sun’s rays for the best
part of the day. It is therefore in the steep roadside banks, in the
sides of the ravines hollowed by the rains in the sandstone, that our
Wasp elects to establish her home. These conditions are common in the
neighbourhood of Carpentras, in the part known as the Hollow Road; and
it is here that I have observed Cerceris tuberculata in her largest
numbers and that I gathered most of my facts relating to her history.
The choice of this vertical site is not enough for her: other
precautions are taken to guard against the inevitable rains of the
season, which is already far advanced. If there be some bit of hard
sandstone projecting like a ledge, if there be naturally hollowed in
the ground some hole large enough to put one’s fist in, it will be
under that shelter or in this cavity that she contrives her gallery,
thus adding a natural vestibule to the edifice of her own construction.
Though no sort of communism exists among them, these insects
nevertheless like to associate in small numbers; and I have always
observed their nests in groups of about ten at least, with the
orifices, which are usually pretty far apart, sometimes close enough to
touch one another.
On a bright, sunny day it is wonderful to watch the different
operations of these industrious miners. Some patiently remove with
their mandibles a few bits of gravel from the bottom of the pit and
push the heavy mass outside; others, scraping the walls of the corridor
with the sharp rakes of their tarsi, collect a heap of rubbish which
they sweep out backwards and send streaming down the sides of the
slopes in a long thread of dust. It was these periodical billows of
sand discharged from the galleries in process of building that betrayed
the presence of my first Cerceres to me and enabled me to discover
their nests. Others, either because they are tired or because they have
finished their hard task, seem to rest and polish their antennæ and
wings under the natural eaves that most frequently protect their
dwelling; or else they remain motionless at the mouth of the hole,
merely showing their wide, square faces, striped black and yellow.
Others, lastly, flit gravely humming on the neighbouring
kermes-oak-bushes, where the males, always on the watch near the
burrows in course of construction, are not slow to join them. Couples
form, often disturbed by the arrival of a second male, who strives to
supplant the happy possessor. The humming becomes threatening, brawls
take place and often the two males roll in the dust until one of them
acknowledges the superiority of his rival. Near by, the female awaits
the outcome of the struggle with indifference; she finally accepts the
male whom the chances of the contest bestow upon her; and the couple
fly out of sight in search of peace and quiet on some distant
brushwood. Here the part played by the males ends. Only half the size
of the females and nearly as numerous, they prowl all around the
burrows, but never enter and never take part in the laborious mining
operations nor in the perhaps even more difficult hunting expeditions
by means of which the cells are to be stocked.
The galleries are ready in a few days, especially as those of the
previous year are employed with the aid of a few repairs. The other
Cerceres, so far as I know, have no fixed home, no family inheritance
handed down from generation to generation. A regular gipsy tribe, they
settle singly wherever the chances of their vagrant life may lead them,
provided that the soil suits them. But the Great Cerceris is faithful
to her household gods. The overhanging blade of sandstone that
sheltered her predecessors is adopted by her in her turn; she digs in
the same layer of sand wherein her forbears dug; and, adding her own
labours to those which went before, she obtains deep retreats that are
not always easy of inspection. The diameter of the galleries is wide
enough to admit a man’s thumb; and the insect moves about in them
readily, even when laden with the prey which we shall see it capture.
Their direction, at first horizontal to a depth of four to eight
inches, describes a sudden bend and dips more or less obliquely now to
this side, now to that. With the exception of the horizontal part and
the bend, the direction of the rest of the tube seems to be regulated
by the difficulties presented by the ground, as is proved by the twists
and turns observed in the more distant portion. The total length of the
shaft attains as much as eighteen inches. At the far end of the tube
are the cells, few in number and each provisioned with five or six
corpses of the Beetle order. But let us leave these building details
and come to facts more capable of exciting our admiration.
The victim which the Cerceris chooses whereon to feed her grubs is a
large-sized Weevil, Cleonus ophthalmicus. We see the kidnapper arrive
heavily laden, carrying her victim between her legs, body to body, head
to head, and plump down at some distance from her hole, to complete the
rest of the journey without the aid of her wings. The Wasp is now
dragging her prey in her mandibles up a vertical, or at least a very
steep surface, productive of frequent tumbles which send kidnapper and
kidnapped rolling helter-skelter to the bottom, but incapable of
discouraging the indefatigable mother, who, covered with dirt and dust,
ends by diving into the burrow with her booty, which she has not let go
for a single moment. Whereas the Cerceris finds it far from easy to
walk with such a burden, especially on ground of this character, it is
a different matter when she is flying, which she does with a vigour
that astonishes us when we consider that the sturdy little creature is
carrying a prize almost as large as herself and heavier. I had the
curiosity to compare the weight of the Cerceris and her victim: the
first turned the scale at 150 milligrammes; [6] the second averaged 250
milligrammes, [7] or nearly double.
These figures are eloquent of the powers of the huntress, nor did I
ever weary of admiring the nimbleness and ease with which she resumed
her flight, with the game between her legs, and rose to a height at
which I lost sight of her whenever, tracked too close by my
indiscretion, she resolved to flee in order to save her precious booty.
But she did not always fly away; and I would then succeed, not without
difficulty, lest I should hurt her, in making her drop her prey by
worrying her and rolling her over. I would then seize the Weevil; and
the Cerceris, thus despoiled, would hunt about here and there, enter
her lair for a moment and soon come out again to fly off on a fresh
chase. In less than ten minutes the skilled huntress had found a new
victim, performed the murder and accomplished the rape, which I often
allowed myself to turn to my own profit. Eight times in succession I
have committed the same robbery at the expense of the same Wasp; eight
times, with unshaken consistency, she has recommenced her fruitless
expedition. Her patience outwore mine; and I left her in undisturbed
possession of her ninth capture.
By this means, or by violating cells already provisioned, I procured
close upon a hundred Weevils; and, notwithstanding what I was entitled
to expect from what Léon Dufour has told us of the habits of the
Buprestis-hunting Cerceris, I could not repress my surprise at the
sight of the singular collection which I had made. Whereas the
Buprestis-slayer, while confining herself to one genus, passes
indiscriminately from one species to another, the more exclusive Great
Cerceris preys invariably on the same species, Cleonus ophthalmicus.
When going through my bag I came upon but one exception, and even that
belonged to a kindred species, Cleonus alternans, a species which I
never saw again in my frequent visits to the Cerceris. Later researches
supplied me with a second exception, in the shape of Bothynoderus
albidus; and that is all. Is this predilection for a single species
adequately explained by the greater flavour and succulence of the prey?
Do the grubs find in this monotonous diet juices which suit them and
which they would not find elsewhere? I do not think so; and, if Léon
Dufour’s Cerceris hunts every sort of Buprestis without distinction,
this is doubtless because all the Buprestes possess the same nutritive
properties. But this must be generally the case with the Weevils also:
their nourishing qualities must be identical; and then this surprising
choice becomes only a question of size and consequently of economy of
labour and time. Our Cerceris, the mammoth of her race, tackles the
Ophthalmic Cleonus by preference because this Weevil is the largest in
our district and perhaps also the commonest. But, if her favourite prey
should fail, she must fall back upon other species, even though they be
smaller, as is proved by the two exceptions stated.
Besides, she is far from being the only one to go hunting at the
expense of the snouted clan, the Weevils. Many other Cerceres,
according to their size, their strength and the accidents of the chase,
capture Weevils varying infinitely in genus, species, shape, and
dimensions. It has long been known that Cerceris arenaria feeds her
grubs on similar provisions. I myself have encountered in her lairs
Sitona lineata, S. tibialis, Cneorinus hispidus, Brachyderes gracilis,
Geonemus flabellipes and Otiorhynchus maleficus. Cerceris aurita is
known to make her booty of Otiorhynchus raucus and Phynotomus
punctatus. The larder of Cerceris Ferreri has shown me the following:
Phynotomus murinus, P. punctatus, Sitona lineata, Cneorinus hispidus,
Rhynchites betuleti. The last, who rolls vine-leaves in the shape of
cigars, is sometimes a superb steel-blue and more ordinarily shines
with a splendid golden copper. I have found as many as seven of these
brilliant insects victualling a single cell; and the gaudiness of the
little subterranean heap might almost stand comparison with the jewels
buried by the Buprestis-huntress. Other species, notably the weaker, go
in for lesser game, whose small size is atoned for by larger numbers.
Thus Cerceris quadricincta stacks quite thirty specimens of Apion
gravidum in each of her cells, without disdaining on occasion such
larger Weevils as Sitona lineata and Phynotomus murinus. A similar
provision of small species falls to the share of Cerceris labiata.
Lastly, the smallest Cerceris in my district, Cerceris Julii, [8]
chases the tiniest Weevils, Apion gravidum and Bruchus granarius,
victims proportioned to the diminutive huntress. To finish with this
list of game, let us add that a few Cerceres observe other gastronomic
laws and raise their families on Hymenoptera. One of these is Cerceris
ornata. We will dismiss these tastes as foreign to the subject in hand.
Of the eight species then of Cerceres whose provisions consist of
Beetles, seven adopt a diet of Weevils and one a diet of Buprestes. For
what singular reasons are the depredations of these Wasps confined to
such narrow limits? What are the motives for this exclusive choice?
What inward likeness can there be between the Buprestes and the
Weevils, outwardly so entirely dissimilar, that they should both become
the food of kindred carnivorous grubs? Beyond a doubt, there are
differences of flavour between this victim and that, nutritive
differences which the larvæ are well able to appreciate; but some
graver reason must overrule all such gastronomic considerations and
cause these curious predilections.
After all the admirable things that have been said by Léon Dufour upon
the long and wonderful preservation of the insects destined for the
flesh-eating larvæ, it is almost needless to add that the Weevils, both
those whom I dug up and those whom I took from between the legs of
their kidnappers, were always in a perfect state of preservation,
though deprived for ever of the power of motion. Freshness of colour,
flexibility of the membranes and the lesser joints, normal condition of
the viscera: all these combine to make you doubt that the lifeless body
before your eyes is really a corpse, all the more as even with the
magnifying-glass it is impossible to perceive the smallest wound; and,
in spite of yourself, you are every moment expecting to see the insect
move and walk. Nay more: in a heat which, in a few hours, would have
dried and pulverized insects that had died an ordinary death, or in
damp weather, which would just as quickly have made them decay and go
mouldy, I have kept the same specimens, both in glass tubes and paper
bags, for more than a month, without precautions of any kind; and,
incredible though it may sound, after this enormous lapse of time the
viscera had lost none of their freshness and dissection was as easily
performed as though I were operating on a live insect. No, in the
presence of such facts, we cannot speak of the action of an antiseptic
and believe in a real death: life is still there, latent, passive life,
the life of a vegetable. It alone, resisting yet a little while longer
the all-conquering chemical forces, can thus preserve the structure
from decomposition. Life is still there, except for movement; and we
have before our eyes a marvel such as chloroform or ether might
produce, a marvel which owes its origin to the mysterious laws of the
nervous system.
The functions of this vegetative life are no doubt enfeebled and
disturbed; but at any rate they are exercised in a lethargic fashion. I
have as a proof the evacuation performed by the Weevils normally and at
intervals during the first week of this deep slumber, which will be
followed by no awakening and which nevertheless is not yet death. It
does not cease until the intestines are emptied of their contents, as
shown by autopsy. Nor do the faint glimmers of life which the insect
still manifests stop at that; and, though irritability of the organs
seems annihilated for good, I have nevertheless succeeded in arousing
slight signs of it. Having placed some recently exhumed and absolutely
motionless Weevils in a bottle containing sawdust moistened with a few
drops of benzine, I was not a little astonished to see their legs and
antennæ moving a quarter of an hour later. For a moment I thought that
I could recall them to life. Vain hope! Those movements, the last
traces of a susceptibility about to be extinguished, soon cease and
cannot be excited a second time. I have tried this experiment in some
cases a few hours after the murderous blow, in others as late as three
or four days after, and always with the same success. Still, the
movement is feeble in proportion to the time that has elapsed since the
fatal stroke. It always spreads from front to back: the antennæ first
wave slowly to and fro; then the front tarsi tremble and take part in
the oscillation; next the tarsi of the second pair of legs and lastly
those of the third pair hasten to do likewise. Once movement sets in,
these different appendages execute their vibrations without any order,
until the whole relapses into immobility, which happens more or less
quickly. Unless the blow has been dealt quite recently, the motion of
the tarsi extends no farther and the legs remain still.
Ten days after an attack I was unable to obtain the least vestige of
susceptibility by the above process; and I then had recourse to the
Voltaic battery. This method is more powerful and provokes muscular
contractions and movements where the benzine-vapour fails. We have only
therefore to apply the current of one or two Bunsen cells through the
conductors of some slender needles. Thrusting the point of one under
the farthest ring of the abdomen and the point of the other under the
neck, we obtain, each time the current is established, not only a
quivering of the tarsi, but a strong reflexion of the legs, which draw
up under the abdomen and then straighten out when the current is turned
off. These flutterings, which are very energetic during the first few
days, gradually diminish in intensity and appear no more after a
certain time. On the tenth day I have still obtained perceptible
movements; on the fifteenth day the battery was powerless to provoke
them, despite the suppleness of the limbs and the freshness of the
viscera. To effect a comparison, I subjected to the action of the
Voltaic pile Beetles really dead, Cellar-beetles, Saperdæ and Lamiæ,
asphyxiated with benzine or sulphuric acid gas. Two hours at most after
the asphyxiation, it was impossible for me to provoke the movements so
easily obtained in Weevils who have already for several days been in
that curious intermediate state between life and death into which their
formidable enemy plunges them.
All these facts are opposed to the idea of something completely dead,
to the theory that we have here a veritable corpse which has become
incorruptible by the action of a preservative fluid. They can be
explained only by admitting that the insect is smitten in the very
origin and mainspring of its movements; that its susceptibility,
suddenly benumbed, dies out slowly, while the more tenacious vegetative
functions die still more slowly and keep the intestines in a state of
preservation for the space of time required by the larvæ.
The particular thing which it was most important to ascertain was the
manner in which the murder is committed. It is quite evident that the
chief part in this must be played by the Cerceris’ venom-laden sting.
But where and how does it enter the Weevil’s body, which is covered
with a hard and well-riveted cuirass? In the various insects pierced by
the assassin’s dart, nothing, even under the magnifying-glass, betrayed
her method. It became a matter, therefore, of discovering the murderous
manœuvres of the Wasp by direct observation, a problem whose
difficulties had made Léon Dufour recoil and whose solution seemed to
me for a time undiscoverable. I tried, however, and had the
satisfaction of succeeding, though not without some preliminary
groping.
When flying from their caverns, intent upon the chase, the Cerceres
would take any direction indifferently, turning now this way, now that;
and they would come back, laden with their prey, from all quarters.
Every part of the neighbourhood must therefore have been explored
without distinction; but, as the huntresses were hardly more than ten
minutes in coming and going, the radius worked could not be one of
great extent, especially when we allow for the time necessary for the
insect to discover its prey, to attack it and to reduce it to an inert
mass. I therefore set myself to inspect the adjacent ground with every
possible attention, in the hope of finding a few Cerceres engaged in
hunting. An afternoon devoted to this thankless task ended by
persuading me of the futility of my quest and of the small chance which
I had of catching in the act a few scarce huntresses, scattered here
and there and soon lost to view through the swiftness of their flight,
especially on difficult ground, thickly planted with vines and
olive-trees. I abandoned the attempt.
By myself bringing live Weevils into the vicinity of the nests, might I
not tempt the Cerceres with a victim all ready to hand and thus witness
the desired tragedy? The idea seemed a good one; and the very next
morning I went off in search of live specimens of Cleonus ophthalmicus.
Vineyards, cornfields, lucerne-crops, hedges, stone-heaps, roadsides: I
visited and inspected one and all; and, after two mortal days of minute
investigation, I was the possessor—dare I say it?—I was the possessor
of three Weevils, flayed, covered with dust, minus antennæ or tarsi,
maimed veterans whom the Cerceres would perhaps refuse to look at! Many
years have passed since the days of that fevered quest when, bathed in
sweat, I made those wild expeditions, all for a Weevil; and, despite my
almost daily entomological explorations, I am still ignorant how and
where the celebrated Cleonus lives, though I meet him occasionally,
roaming on the edge of the paths. O wonderful power of instinct! In the
selfsame places and in a mere fraction of time, our Wasps would have
found by the hundred these insects undiscoverable by man; and they
would have found them fresh and glossy, doubtless just issued from
their nymphal cocoons!
No matter, let us see what we can do with my pitiful bag. A Cerceris
has just entered her gallery with her usual prey; before she comes out
again for a new expedition, I place a Weevil a few inches from the
hole. The insect moves about; when it strays too far, I restore it to
its position. At last the Cerceris shows her wide face and emerges from
the hole; my heart beats with excitement. The Wasp stalks about the
approaches to her home for a few moments, sees the Weevil, brushes
against him, turns round, passes several times over his back and flies
away without honouring my capture with a touch of her mandibles: the
capture which I was at such pains to acquire. I am confounded, I am
floored. Fresh attempts at other holes lead to fresh disappointments.
Clearly these dainty sports-women will have none of the game which I
offer them. Perhaps they find it uninteresting, not fresh enough.
Perhaps, by taking it in my fingers, I have given it some odour which
they dislike. With these epicures a mere alien touch is enough to
produce disgust.
Should I be more fortunate if I obliged the Cerceris to use her sting
in self-defence? I enclosed a Cerceris and a Cleonus in the same bottle
and stirred them up by shaking it. The Wasp, with her sensitive nature,
was more impressed than the other prisoner, with his dull and clumsy
organization; she thought of flight, not of attack. The very parts were
interchanged: the Weevil, becoming the aggressor, at times seized with
his snout a leg of his mortal enemy, who was so greatly overcome with
fear that she did not even seek to defend herself. I was at the end of
my resources; yet my wish to behold the catastrophe was but increased
by the difficulties already experienced. Well, I would try again.
A bright idea flashed across my mind, entering so naturally into the
very heart of the question that it brought hope in its train. Yes, that
must be it; the thing was bound to succeed. I must offer my scorned
game to the Cerceris in the heat of the chase. Then, carried away by
her absorbing preoccupation, she would not perceive its imperfections.
I have already said that, on her return from hunting, the Cerceris
alights at the foot of the slope, at some distance from the hole,
whither she laboriously drags her prey. It became a matter, therefore,
of robbing her of her victim by drawing it away by one foot with my
forceps and at once throwing her the live Weevil in exchange. The trick
succeeded to perfection. As soon as the Cerceris felt her prey slip
from under her belly and escape her, she tapped the ground impatiently
with her feet, turned round and, perceiving the Weevil that had taken
the place of her own, flung herself upon him and clasped him in her
legs to carry him away. But she soon became aware that her prey was
alive; and now the tragedy began, only to end with inconceivable
rapidity. The Wasp faced her victim and, gripping its snout with her
powerful mandibles, soon had it at her mercy. Then, while the Weevil
reared on his six legs, the other pressed her forefeet violently on his
back, as if to force open some ventral joint. I next saw the assassin’s
abdomen slip under the Cleonus’ belly, bend into a curve, and dart its
poisoned lancet briskly, two or three times, into the joint of the
prothorax, between the first and second pair of legs. All was over in a
moment. Without the least convulsive movement, without any of that
stretching of the limbs which accompanies an animal’s death, the victim
fell motionless for all time, as though struck by lightning. It was
terribly and at the same time wonderfully quick. The murderess next
turned the body on its back, placed herself belly to belly with it,
with her legs on either side, clasped it and flew away. Thrice over I
renewed the experiment, with my three Weevils; and the process never
varied.
Of course I gave the Cerceris back her first prey each time and
withdrew my own Cleonus to examine him at my leisure. The inspection
but confirmed my high opinion of the assassin’s formidable skill. It
was impossible to perceive the least sign of a wound, the slightest
flow of vital fluid at the point attacked. But what was most
striking—and justly so—was the prompt and complete annihilation of all
movement. Immediately after the murder I sought in vain for traces of
irritability of the organs in the three Weevils dispatched before my
eyes: those traces were never revealed, whether I pinched or pricked
the insect; and it required the artificial means described above to
provoke them. Thus these powerful Cleoni, which, if pierced alive with
a pin and fixed on the insect-collector’s fatal sheet of cork, would
have kicked and struggled for days and weeks, nay, for whole months on
end, instantly lose all power of movement from the effect of a tiny
prick which inoculates them with an invisible drop of venom. But
chemistry has no poison so potent in so minute a dose; prussic acid
would hardly produce those effects, if indeed it can produce them at
all. It is not to toxology then, surely, but to physiology and anatomy
that we must turn to grasp the cause of this instantaneous
annihilation; and to understand these marvellous happenings we must
consider not so much the intense strength of the poison injected as the
importance of the organ injured.
What is there, then, at the point where the sting enters?