CERCERIS TUBERCULATA

With my mind full of the great deeds of the Buprestis hunter, I watched

for an opportunity of observing in my turn the labours of the Cerceris,

and I watched so closely that finally I got my chance. True, it was not

the Hymenopteron celebrated by Dufour, with such sumptuous provisions

that when dug up they made one think of the powder from a nugget broken

by the miner’s pickaxe in some gold field: it was a closely related

species, a giant brigand which contents itself with more modest prey—in

short, Cerceris tuberculata or C. major, the largest and strongest of

the genus.

The last fortnight in September is the time when our Hymenopteron makes

its burrows, and buries in the depths the prey destined for its brood.

The position of the domicile, always sagaciously chosen, is governed by

those mysterious laws varying with the species, but unchangeable for

any one of them. The Cerceris of Léon Dufour requires a horizontal,

beaten, compact soil, like that of a path, to avoid landslips and

changes which would ruin its gallery with the first rain. Ours, on the

contrary, selects vertical ground. By this slight architectural

modification she avoids most of the dangers which might threaten her

tunnel; therefore she is not particular as to the nature of the soil,

and hollows her gallery either in friable earth with a little clay, or

in the crumbling soil of the Mollasse, which makes the labour of

excavation much easier. The only indispensable condition seems to be

that the soil should be dry, and exposed to the sun for the greater

part of the day. It is therefore in the steep bank along a road, and in

the sides of hollows made by rain in the sandy Mollasse, that our

Hymenopteron makes its abode. Such conditions are frequent near

Carpentras in what is known as the hollow way, and it is there that I

have found C. tuberculata in the greatest abundance, and have collected

most of the facts relating to its history.

It is not enough to choose this vertical situation; other precautions

are taken to guard against the already advanced season. If some bit of

hard sandstone project like a shelf, or if a hole the size of one’s

fist should have been hollowed naturally in the ground, it will be

under this shelter or in this cavity that the gallery is made, a

natural vestibule being thus added by the Cerceris to its own edifice.

Although there is no kind of community among them, these insects like

to associate in small parties, and I have always found their nests in

groups of about ten, with orifices, though usually far apart, sometimes

touching.

When the sun shines it is wonderful to see the ways of these

hard-working miners. Some patiently extract bits of gravel from the

bottom of a hole with their mandibles, and push out the heavy mass;

others scratch the walls of their tunnel with the sharp rakes of their

tarsi, forming a heap of rubbish which they sweep out backward, and

send sliding down the steep incline in long dusty streams. It was these

periodical sand waves thrown out of galleries in process of

construction which betrayed my first Cerceris, and led to the discovery

of the nests. Others, either weary, or having completed their hard

task, rested and polished their antennæ and wings under the natural

caves which usually protect their dwelling, or else sat motionless at

the mouth of their holes, only displaying their wide, square faces,

barred with yellow and black. Others again were flying with a deep hum

on the bushes near the cochineal oak, where the males, always on the

watch near the burrows in process of construction, speedily join them.

Couples form, often troubled by the arrival of a second male, which

tries to supplant the happy possessor. The humming grows menacing,

quarrels begin, and often both males roll in the dust until one

acknowledges the superiority of his rival. Not far off the female waits

with indifference the upshot of the struggle, accepting finally the

male bestowed on her by the chances of the fight, and the pair fly out

of sight to seek peace in some distant thicket. Here the part of the

male ends. One half smaller than the females, they prowl about the

burrows but never enter, and never take any part in the hard work of

excavation, or that perhaps yet harder of provisioning the cells.

In a few days the galleries are ready, especially as after some repairs

those of the preceding year are used again. Other Cerceris, as far as I

know, have no fixed home, transmitted from one generation to another.

True Bohemians, they establish themselves wherever the chances of their

vagabond life may lead them, so long as the soil suits them. But C.

tuberculata is faithful to her penates. The projecting shelf of

sandstone used by its predecessors is used again; it hollows out the

same layer of sand hollowed by its forbears, and, adding its own labour

to theirs, obtains deep-seated retreats sometimes only visited with

difficulty. The diameter of the galleries would admit a thumb, and the

insect can move about easily, even when laden with the prey which we

shall see it capture. Their direction is horizontal, from four to eight

inches, then makes a sudden turn downward more or less obliquely, now

in one direction, now in another. Except the horizontal part, and the

angle of the tunnel, the direction seems to depend on the difficulties

of the ground, as is proved by the windings and changes in the farthest

part of this kind of canal, which is half a yard in length. At the far

end are the cells, not numerous, and provisioned with five or six dead

beetles. But let us leave the details of how a Cerceris builds, and

turn to more wonderful facts.

The victim chosen to feed the larvæ is a large weevil (Cleonus

ophthalmicus). One sees the captor arrive, carrying the victim between

its feet, body to body, head to head. It alights heavily some way from

the hole to complete the journey without the aid of wings, and drags

the prey laboriously with its jaws, on ground if not vertical, at least

very steeply inclined, which often results in sending captor and

captive headlong to the bottom, but the indefatigable mother finally

darts into her burrow, covered with dust, but with the prey of which

she has never let go. If she does not find walking with such a burden

easy, it is otherwise with her flight, which is surprisingly powerful,

if one considers that the strong little creature is carrying a prey

nearly as large as and heavier than herself. I have had the curiosity

to weigh the Cerceris and her prey separately, and the first weighed

150 milligrammes, and the second about 250, almost double.

These weights speak eloquently for the vigorous huntress, and I never

wearied of watching how swiftly and easily she resumed her flight, and

rose out of sight with the game between her feet when approached too

closely. But she did not always fly away, and then, though it was

difficult to do so, and yet avoid hurting her, I would make her drop

the prey by worrying and upsetting her with a straw. Then I would take

possession of the victim, and the Cerceris, thus despoiled, would hunt

about, go into her hole for a moment, come out, and resume the chase.

In less than ten minutes the sharp-sighted insect would find a new

victim, murder it and carry it off, not seldom to my profit. Eight

times running have I stolen from the same individual; eight times did

the indefatigable Cerceris resume her fruitless journey. Her

perseverance tired out mine, and I let her keep the ninth capture.

By this means, and by breaking open cells already filled with

provisions, I got nearly a hundred weevils, and in spite of what I had

a right to expect from what Léon Dufour has told us of the habits of

the Cerceris bupresticida, I could not repress my astonishment at the

sight of the singular collection which I had made. His Cerceris, though

it limits itself to one genus, yet takes any species within that limit,

but the more exclusive C. tuberculata preys exclusively on Cleonus

ophthalmicus. On looking through my booty I met with but one single

exception, and that belonged to a closely allied species, C.

alternans—one which I never met with again in my frequent visits to the

Cerceris. Later researches furnished me with a second exception,

Bothynoderes albidus, and these are all. Can a specially succulent and

savoury prey explain this predilection for a single species? Do the

larvæ find in this unvaried diet juices which suit them peculiarly, and

which they would not find elsewhere? I do not think so, and if Léon

Dufour’s Cerceris hunted all the kinds of Buprestids, no doubt it was

because they all have the same nutritive properties. But this must

generally be the case with all the Curculionidæ; their alimentary

properties must be identical, and in that case this amazing choice can

only be one of size, and therefore of economy of labour and time. Our

Cerceris, the giant of its race, chooses C. ophthalmicus as the largest

in our district, and perhaps the commonest. But if this favourite prey

fail, it must fall back upon other species, even if smaller, as is

proved by the two exceptions above mentioned.

Moreover, it is by no means the only one to hunt the long-nosed class

of weevils. Many other Cerceris, according to their size, strength, and

the chances of the chase, capture Curculionidæ most various in genus,

species, shape, and size. It has long been known that Cerceris arenaria

feeds her young with similar food. I myself have found in its burrows

Sitona lineata, S. tibialis, Cneorhinus hispidus, Brachyderes gracilis,

Geonemus flabellipes, Otiorhynchus maleficus. Cerceris aurita is known

to prey on Otiorhynchus raucus and Phytonomus punctatus. In the larder

of Cerceris ferreri I saw Phytonomus murinus, P. punctatus, Sitona

lineata, Cneorhinus hispidus, Rhynchites betuleti. This weevil, which

rolls up vine leaves into the shape of cigars, is sometimes of a superb

metallic blue, but more usually of a splendid golden copper. I have

found as many as seven of these brilliant insects laid up in one cell,

and the gorgeous colours of the little heap might almost bear

comparison with the jewels buried by the huntress of the Buprestids.

Other species, especially the weaker, hunt smaller game, the lesser

size being compensated by numbers. Thus, Cerceris quadricincta heaps in

each cell some thirty Apion gravidum, but does not disdain on occasion

bigger weevils, such as Sitona lineata, Phytonomus murinus. Cerceris

labiata also lays up small species. Finally, the smallest Cerceris in

my part of France, C. julii, hunts the least weevils, Apion gravidum

and Bruchus granarius, game proportioned to its own size. To end this

list of provender, let us add that some Cerceris follow other

gastronomic laws, and bring up their families on Hymenoptera. Such is

C. ornata. These tastes being alien to our subject, let us pass on.

We see that out of eight species of Cerceris which lay up Coleoptera as

food, seven hunt weevils and one Buprestids. What singular reason

confines the chase of these Hymenoptera within such narrow limits? What

are the motives of such an exclusive selection? What internal likeness

is there between the Buprestids and the weevils, outwardly quite

dissimilar, that both should become food for carnivorous and nearly

related larvæ? No doubt between such and such a victim there are

differences as to taste and nutritive qualities which the larvæ

thoroughly appreciate, but there must be a far graver reason than these

gastronomic considerations to explain these strange predilections.

After all that has been so admirably said by Léon Dufour on the long

and marvellous preservation of the insects destined as food for the

carnivorous larvæ, it is needless to say that the weevils which I dug

up, as well as those taken from between the feet of their murderer,

were perfectly fresh, though permanently motionless. Freshness of

colour, suppleness of the membranes and smallest articulations, normal

condition of the viscera, all combine to make one doubt whether the

inert body under one’s eyes can really be a corpse, all the more that

even under the magnifying glass it is impossible to perceive the

smallest wound; and in spite of one’s self one expects every moment to

see the insect move and walk. Yet more, in weather so hot that insects

which had died naturally would in a few hours have become dried up and

crumbly, or again in damp weather which would with equal rapidity have

made them decay and grow mouldy. I have kept specimens in glass tubes

or cones of paper over a month with no precautions, and wonderful to

say, after all this length of time, the intestines were as fresh as

ever, and I found dissection as easy as if the creatures were alive.

No, in presence of such facts one cannot talk of an antiseptic, and

believe in real death; life is still there—life latent and

passive—vegetative life. It alone, struggling successfully for a time

against the destructive invasion of chemical forces, can thus preserve

the organism from decomposition. Life is still there, but without

motion, and we have under our eyes such a marvel as chloroform or ether

might produce—a marvel caused by the mysterious laws of the nervous

system.

The functions of this vegetative life are slackened and troubled no

doubt, but still they are feebly exercised. I have the proof of this in

that action of the viscera which takes place normally and at intervals

in the weevils during the first week of that deep slumber, which will

never be broken, and yet which is not death. It only ceases when the

intestine is empty, as is shown by autopsy. But the faint rays of life

which the creature manifests do not stop there; and though sensation

appears annihilated for ever, I have succeeded in reawakening some

vestige of them. Having placed weevils, recently exhumed and absolutely

motionless, in a bottle with sawdust moistened with benzine, I was not

a little surprised to see a quarter of an hour later moving antennæ and

feet. For a moment I thought I could recall them to life. Vain hope!

these movements, last trace of a sensitiveness about to cease, soon

stopped, and could not be excited a second time. I have repeated this

experiment from some hours to several days after the murder, and always

with the same success; only movement is tardy in appearing in

proportion as the date of the victim’s death is distant. The movements

are always from the forepart backward. First, the antennæ move, then

the front tarsi tremble and share in the oscillations; next, the second

pair do the same; and finally, the third. Once movement is excited, all

these members oscillate without any order until all become again

motionless, as they do sooner or later. Unless death has been quite

recent, movement does not go beyond the tarsi, and the legs remain

motionless.

Ten days after the murder I could not obtain the least sign of

irritability by the proceeding described, and I had recourse to the

Voltaic battery. This is more effective, and provokes muscular

contractions where the vapour of benzine fails. One or two elements of

Bunsen suffice, which are armed with the rheophores of slender needles.

Plunging the point of the one under the furthest ring of the abdomen,

and the point of the other under the neck, you obtain each time that

the current is established, not only the quivering of the tarsi, but a

strong flexion of the feet, which fold themselves under the body, and

relax when the current is interrupted. These movements, very energetic

during the first days, gradually lose intensity, and after a certain

time appear no more. On the tenth day I have still been able to obtain

visible motions, but on the fifteenth the pile was unable to provoke

them, notwithstanding the suppleness of the limbs and freshness of the

viscera. I have submitted also to the action of the pile Coleoptera

really dead, Blaps, Saperda, Lamia, asphyxiated by benzine or

sulphureous gas, and two hours later it was impossible to provoke the

movements obtained so easily from weevils lying already for several

days in the singular state, intermediate between life and death, into

which their redoubtable enemy plunges them.

All these facts contradict the supposition of an animal completely

dead, and the hypothesis of a real corpse rendered incorruptible by

some antiseptic liquid. One can only explain them by admitting that the

animal is struck in the principle of its movements, and that

sensitiveness, suddenly benumbed, dies slowly out, while the more

tenacious, vegetative functions die yet more slowly and preserve the

intestines during the time necessary for the larva.

The most important detail to show was how the murder is committed.

Evidently, the chief part must be played by the poisoned dart of the

Cerceris. But where and how does it penetrate the body of the weevil,

covered with a hard cuirass, with pieces so closely joined? Even under

the magnifying glass nothing told where the sting entered. Direct

examination, therefore, was required to discover the murderous ways of

the Cerceris—a problem before whose difficulties Léon Dufour had

already recoiled, and the solution of which seemed to me for a time

impossible. I tried, however, and had the satisfaction of succeeding,

though not without some groping about.

When they fly from their holes to the chase, the Cerceris go here and

there, sometimes on one side, sometimes on the other, and return from

all directions, loaded with prey, so that they must seek it on all

sides; but as they barely take ten minutes between going and returning,

the space worked over could not be very great, especially considering

the time necessary to discover the prey, to attack and render it an

inert mass. I, therefore, set myself to examine all the adjacent ground

with close attention, hoping to discover some Cerceris on the hunt. One

afternoon devoted to this weary work convinced me of the uselessness of

my researches, and of the little chance I had of surprising any of the

few Cerceris, scattered here and there, and soon lost to view by their

rapid flight; above all, in difficult ground, planted with olives, I

gave up the attempt. But by carrying live weevils to the neighbourhood

of the nests might I not tempt the Cerceris by a prey found without

trouble, and so observe the drama? The notion seemed good, and the very

next day I set out to find live Cleonus ophthalmicus. Vineyards,

wheat-fields, and crops of lucerne, and heaps of stones did I visit and

examine one and all, and after two days of close search I

possessed—dare I own it?—three weevils! bare, dusty, maimed of antennæ

or tarsi, shabby old creatures which, perhaps, the Cerceris would not

touch! Since the day of that fevered search, when, for a weevil’s sake,

I bathed myself in perspiration during my wild expedition, many a year

has passed, and yet, in spite of almost daily entomological researches,

I am still ignorant of the life and habits of this Cleonus, which I met

here and there, straying on the edge of paths. Wonderful powers of

instinct! in the same spots, and in a fraction of time, one

Hymenopteron would have found hundreds of these insects which man

cannot find, and found them fresh and shining, no doubt just emerged

from the cocoon!

No matter; let us experiment with my wretched victim. A Cerceris has

just gone into her gallery with her prey; before she comes out for a

new expedition I place a weevil a few inches from her hole. The weevil

moves about; when it strays too far I bring it back to its place. At

last the Cerceris shows her wide face at the mouth of her hole; my

heart beats fast. She walks for a few minutes near her dwelling, sees

the weevil, brushes against it, turns, passes several times over its

back, and flies off without even honouring my captive with a bite—my

captive which cost me so much labour! I was confounded—knocked over.

New attempts at other holes, new disappointments. Decidedly these

dainty hunters will have none of the game which I offer them. Perhaps

they find it too old, too tasteless; perhaps, in handling it, I

communicated some smell to it which displeases them. Foreign contact

disgusts these connoisseurs.

Should I be more fortunate if I obliged the Cerceris to defend herself?

I enclosed one with a Cleonus in a bottle, irritating them by shaking

it. The Hymenopteron, sensitive by nature, was more impressed than the

other prisoner, with its dull, heavy organisation; she thought of

escape, not attack. Their parts were exchanged; the weevil became the

aggressor, sometimes seizing with the end of its trunk a foot of its

mortal foe, who made no attempt at defence, so terrified was she. I

could devise nothing more; my desire to be present at the dénoûment had

only added to former difficulties. Well, let us try again.

A luminous idea flashed upon me, bringing hope, so naturally did it

touch the very heart of the question. Of course, it was the right thing

and must succeed. My disdained game must be offered to the Cerceris in

the heat of the chase—then, absorbed and preoccupied, she will not

discover its imperfections. I have already said that on returning from

the chase the Cerceris alights at the foot of the incline at some

distance from the hole, whither she laboriously drags the prey. What I

then had to do was to deprive her of her victim, drawing it away by one

foot with pincers, and instantly throwing her the living weevil in

exchange. This manœuvre succeeded perfectly. As soon as the Cerceris

felt the prey slip under her body and escape her, she stamped with

impatience, turned round, and perceiving the weevil which had replaced

hers, flung herself upon it and clasped it in order to carry it away.

But she promptly perceived that this prey was alive, and then the drama

began and ended with inconceivable rapidity. The Cerceris faced her

victim, seized its proboscis with her powerful jaws and grasped it

vigorously, and while the weevil reared itself up, pressed her forefeet

hard on its back as if to force open some ventral articulation. Then

the tail of the murderess slid under the Cleonus, curved and darted its

poisoned lancet swiftly two or three times at the joining of the

prothorax, between the first and second pair of feet. In a twinkling

all was over. Without one convulsive movement, with no motion of the

limbs such as accompany the death of an animal, the victim fell

motionless for ever, as if annihilated. It was at once wonderful and

terrible in its rapidity. Then the assassin turned the Weevil on its

back, placing herself body to body with it, her legs on either side of

it, and flew off. Three times I renewed the experiment with my three

Weevils, and the same scene was always enacted.

Of course, each time I gave the Cerceris back her first prey and

withdrew my Cleonus to examine it at greater leisure. This examination

only confirmed my opinion of the terrible skill of the assassin. It is

impossible to find the slightest trace of a wound, or the smallest flow

of vital liquids from the point which was struck. But the most striking

thing is the rapid, complete annihilation of all movement. Vainly did I

seek even immediately after the murder for any trace of sensibility in

the three Weevils done to death under my eyes—neither pinching nor

pricking provoked it; to do so required the artificial means already

mentioned. Thus these robust Cleonus, which, pierced alive with a pin

and fixed by a collector on his fatal sheet of cork, would have

struggled for days, weeks, nay, whole months, instantly lose all power

of motion from the effect of a little prick which inoculates them with

a minute drop of poison. Chemistry knows none so active in so small a

dose; scarcely could prussic acid produce such an effect, if, indeed,

it could do so at all. It is not then to toxology, but to physiology

and anatomy that we must turn to find the cause of such instantaneous

catalepsy; it is not so much the great virulence of the poison

injected, as the importance of the organ injured by it which we must

consider in order to explain these marvels. What, then, is found at the

point where the sting penetrates?

V