A PARASITE OF THE MAGGOT
The dangers of the exhumation are not the only ones; the Bluebottle
must be acquainted with others. Life, when all is said, is a
knacker's yard wherein the devourer of today becomes the devoured
of tomorrow; and the robber of the dead cannot fail to be robbed of
her own life when the time comes. I know that she has one
exterminator in the person of the tiny Saprinus beetle, a fisher of
fat sausages on the edge of the
pools formed by liquescent corpses.
Here swarm in common the grubs of the greenbottle, the flesh fly
and the bluebottle. The Saprinus draws them to him from the bank
and gobbles them indiscriminately. They represent to him morsels
of equal value.
This banquet can be observed only in the open country, under the
rays of a hot sun. Saprini and greenbottles never enter our
houses; the flesh fly visits us but discreetly, does not feel at
home with us; the only one who comes fussing along is the
bluebottle, who thus escapes the tribute due to the consumer of
plump sausages. But, in the fields, where she readily lays her
eggs upon any carcass that she finds, she, as well as the others,
sees her vermin swept away by the gluttonous Saprinus.
In addition, graver disasters decimate her family, if, as I do not
doubt, we can apply to the bluebottle what I have seen happen in
the case of her rival, the flesh fly. So far, I have had no
opportunity of actually perceiving with the first what I have to
tell of the second; still, I do not hesitate to repeat about the
one what observation has taught me about the other, for the larval
analogies between the two flies are very close.
Here are the facts. I have gathered a number of pupae of the flesh
fly in one of my vermin jars. Wishing to examine the pupa's hinder
end, which is hollowed into a cup and scalloped into a coronet, I
stave in one of the little barrels and force open the last segments
with the point of my pocketknife. The horny keg does not contain
what I expected to find: it is full of tiny grubs packed one atop
the other with the same economy of space as anchovies in a bottle.
Save for the skin, which has hardened into a brown shell, the
substance of the maggot has disappeared, changed into a restless
There are thirty-five occupants. I replace them in their casket.
The rest of my harvest, wherein, no doubt, are other pupae
similarly stocked, is arranged in tubes that will easily show me
what happens. The thing to discover is what genus of parasites the
grubs enclosed belong to. But it is not difficult, without waiting
for the hatching of the adults, to recognize their nature merely by
their mode of life. They form part of the family of Chalcididae,
who are microscopic ravagers of living entrails.
Not long ago, in winter, I took from the chrysalis of a great
peacock moth four hundred and forty-nine parasites belonging to the
same group. The whole substance of the future moth had
disappeared, all but the nymphal wrapper, which was intact and
formed a handsome Russia-leather wallet. The worm grubs were here
heaped up and squeezed together to the point of sticking to one
another. The hair pencil extracts them in bundles and cannot
separate them without some difficulty. The holding capacity is
strained to the utmost; the substance of the vanished Moth would
not fill it better. That which died has been replaced by a living
mass of equal dimensions, but subdivided. The price of this
colony's existence is the conversion of the chrysalis into a sort
of milk food of doubtful constitution. The enormous udder has been
You shudder when you think of that budding flesh nibbled bit by bit
by four or five hundred gormandizers; the horrified imagination
refuses to picture the anguish suffered by the tortured wretch.
But is there really any pain? We have leave to doubt it. Pain is
a patent of nobility; it is more pronounced in proportion as the
sufferer belongs to a higher order. In the lower ranks of animal
life, it must be greatly reduced, perhaps even nil, especially when
life, in the throes of evolution, has not yet acquired a stable
equilibrium. The white of an egg is living matter, but endures the
prick of a needle without a quiver. Would it not be the same with
the chrysalis of the great peacock, dissected cell by cell by
hundreds of infinitesimal anatomists? Would it not be the same
with the pupa of the flesh fly? These are organisms put back into
the crucible, reverting to the egg state for a second birth. There
is reason to believe, therefore, that their destruction crumb by
crumb is merciful.
Towards the end of August, the parasite of the flesh fly's grubs
makes her appearance out of doors in the adult form. She is a
Chalcidid, as I expected. She issues from the barrel through one
or two little round holes which the prisoners have pierced with a
patient tooth. I count some thirty to each pupa. There would not
be enough room in the abode if the family were larger.
The imp is a slim and elegant creature, but oh, how small! She
measures hardly two millimeters. Her garb is bronzed black, with
pale legs and a heart shaped, pointed, slightly pedunculate
abdomen, with never a trace of a probe for inoculating the eggs.
The head is transversal, the width exceeding the length.
The male is only half the size of the female; he is also very much
less numerous. Perhaps pairing is here, as we see elsewhere, a
secondary matter from which it is possible to abstain, in part,
without injuring the prospects of the race. Nevertheless, in the
tube wherein I have housed the swarm, the few males lost among the
crowd ardently woo the passing fair. There is much to be done
outside, as long as the flesh fly's season lasts; things are
urgent; and each pigmy hurries as fast as she can to take up her
part as an exterminator.
How is the parasite's inroad into the flesh fly's pupae effected?
Truth is always veiled in a certain mystery. The good fortune that
secured me the ravaged pupa taught me nothing concerning the
tactics of the ravager. I have never seen the Chalcidid explore
the contents of my appliances; my attention was engaged elsewhere
and nothing is so difficult to see as a thing not yet suspected.
But, though direct observation be lacking, logic will tell us
approximately what we want to know.
It is evident, to begin with, that the invasion cannot have been
made through the sturdy amour of the pupae. This is too hard to be
penetrated by the means at the pigmy's disposal. Naught but the
delicate skin of the maggots lends itself to the introduction of
the germs. An egg laying mother, therefore, appears, inspects the
surface of the pool of sanies swarming with grubs, selects the one
that suits her and perches on it; then, with the tip of her pointed
abdomen, whence emerges, for an instant, a short probe kept hidden
until then, she operates on the patient, perforating his paunch
with a dexterous wound into which the germs are inserted.
Probably, a number of pricks are administered, as the presence of
thirty parasites seems to demand.
Anyway, the maggot's skin is pierced at either one point or many;
and this happens while the grub is swimming in the pools formed by
the putrid flesh. Having said this, we are faced with a question
of serious interest. To set it forth necessitates a digression
which seems to have nothing to do with the subject in hand and is
nevertheless connected with it in the closest fashion. Without
certain preliminaries, the remainder would be unintelligible. So
now for the preliminaries.
I was in those days busy with the poison of the Languedocian
scorpion and its action upon insects. To direct the sting toward
this or the other part of the victim and moreover to regulate its
emission would be absolutely impossible and also very dangerous, as
long as the scorpions were allowed to act as they pleased. I
wished to be able myself to choose the part to be wounded; I
likewise wished to vary the dose of poison at will. How to set
about it? The scorpion has no jarlike receptacle in which the
venom is accumulated and stored, like that possessed, for instance,
by the wasp and the bee. The last segment of the tail, gourd
shaped and surmounted by the sting, contains only a powerful mass
of muscles along which lie the delicate vessels that secrete the
In default of a poison jar which I would have placed on one side
and drawn upon at my convenience, I detach the last segment,
forming the base of the sting. I obtain it from a dead and already
withered scorpion. A watch glass serves as a basin. Here, I tear
and crush the piece in a few drops of water and leave it to steep
for four-and-twenty hours. The result is the liquid which I
propose to use for the inoculation. If any poison remained in my
animal's caudal gourd, there must be at least some traces of it in
the infusion in the watch glass.
My hypodermic syringe is of the simplest. It consists of a little
glass tube, tapering sharply at one end. By drawing in my breath,
I fill it with the liquid to be tested; I expel the contents by
blowing. Its point is almost as fine as a hair and enables me to
regulate the dose to the degree which I want. A cubic millimeter
is the usual charge. The injection has to be made at parts that
are generally covered with horn. So as not to break the point of
my fragile instrument, I prepare the way with a needle, with which
I prick the victim at the spot required. I insert the tip of the
loaded injector in the hole thus made and I blow. The thing is
done in a moment, very neatly and in an orthodox fashion, favorable
to delicate experiments. I am delighted with my modest apparatus.
I am equally delighted with the results. The scorpion himself,
when wounding with his sting, in which the poison is not diluted as
mine is in the watch glass, would not produce effects like those of
my pricks. Here is something more brutal, producing more
convulsion in the sufferer. The virus of my contriving excels the
The test is several times repeated, always with the same mixture,
which, drying up by spontaneous evaporation, then made to serve
again by the addition of a few drops of water, once more drained
and once more moistened, does duty for an indefinite length of
time. Instead of abating, the virulence increases. Moreover, the
corpses of the insects operated upon undergo a curious change,
unknown in my earlier observations. Then the suspicion comes to me
that the actual poison of the scorpion does not enter into the
matter at all. What I obtain with the end joint of the tail, with
the gland at the base of the sting, I ought to obtain with any
other part of the animal.
I crush in a few drops of water a joint of the tail taken from the
front portion, far from the poison glands. After soaking it for
twenty-four hours, I obtain a liquid whose effects are absolutely
the same as those before, when I used the joint that bears the
sting. I try again with the scorpion's claws, the contents of
which consist solely of muscle. The results are just the same.
The whole of the animal's body, therefore, no matter which fragment
be submitted to the steeping process, yields the virus that so
greatly pricks my curiosity.
Every part of the Spanish fly [Cantharis or blistering beetle],
inside and out, is saturated with the blistering element; but there
is nothing like this in the scorpion, who localizes his venom in
his caudal gland and has none of it elsewhere. The cause of the
effects which I observe is therefore connected with general
properties which I ought to find in any insect, even the most
I consult Oryctes nasicornis, the peaceable rhinoceros beetle, on
this subject. To get at the exact nature of the materials, instead
of pulverizing the whole insect in a mortar, I use merely the
muscular tissue obtained by scraping the inside of the dried
Oryctes' corselet. Or else I extract the dry contents of the hind
legs. I do the same with the desiccated corpses of the cockchafer,
the Capricorn, or Cerambyx beetle, and the Cetonia, or rosechafer.
Each of my gleanings, with a little water added, is left to soften
for a couple of days in a watch glass and yields to the liquid
whatever can be extracted from it by crushing and dissolving.
This time, we take a great step forward. All my preparations,
without distinction, are horribly virulent. Let the reader judge.
I select as my first patient the sacred beetle, Scarabaeus sacer,
who thanks to his size and sturdiness, lends himself admirably to
an experiment of this kind. I operate upon a dozen, in the
corselet, on the breast, on the belly and, by preference, on one of
the hind legs, far removed from the impressionable nervous centers.
No matter what part my injector attacks, the effect produced is the
same, or nearly. The insect falls as though struck by lightning.
It lies on its back and wriggles its legs, especially the hind
legs. If I set it on its feet again, I behold a sort of St.
Vitus' dance. Scarabaeus lowers his head, arches his back, draws
himself up on his twitching legs. He marks time with his feet on
the ground, moves forward a little, moves as much backward, leans
to the right, leans to the left, in wild disorder, incapable of
keeping his balance or making progress. And this happens with
sudden jerks and jolts, with a vigor no whit inferior to that of
the animal in perfect health. It is a displacement of all the
works, a storm that uproots the mutual relations of the muscles.
Seldom have I witnessed such sufferings, in my career as a cross-
examiner of animals and, therefore, as a torturer. I should feel a
scruple, did I not foresee that the grain of sand shifted today may
one day help us by taking its place in the edifice of knowledge.
Life is everywhere the same, in the Dung beetle's body as in man's.
To consult it in the insect means consulting it in ourselves, means
moving towards vistas which we cannot afford to neglect. That hope
justifies my cruel studies, which, though apparently so puerile,
are in reality worthy of serious consideration.
Of my dozen sufferers, some rapidly succumb, others linger for a
few hours. They are all dead by tomorrow. I leave the corpses on
the table, exposed to the air. Instead of drying and stiffening,
like the asphyxiated insects intended for our collections, my
patients, on the contrary, turn soft and slacken in the joints,
notwithstanding the dryness of the surrounding air; they become
disjointed and separate into loose pieces, which are easily
The results are the same with the Capricorn, the cockchafer, the
Procrustes [a large ground beetle], the Carabus [the true ground
beetle, including the gold beetle]. In all of them there is a
sudden break-up, followed by speedy death, a slackening of the
joints and swift putrefaction. In a non-horny victim, the quick
chemical changes of the tissues are even more striking. A Cetonia
grub, which resists the scorpion's sting, even though repeatedly
administered, dies in a very short time if I inject a tiny drop of
my terrible fluid into any part of its body. Moreover, it turns
very brown and, in a couple of days, becomes a mass of black
The great peacock, that large moth who recks little of the
scorpion's poison, is no more able to resist my inoculations than
the sacred beetle and the others. I prick two in the belly, a male
and a female. At first, they seem to bear the operation without
distress. They grip the trellis work of the cage and hang without
moving, as though indifferent. But soon the disease has them in
its grip. What we see is not the tumultuous ending of the sacred
beetle; it is the calm advent of death. With wings slackly
quivering, softly they die and drop from the wires. Next day, both
corpses are remarkably lax; the segments of the abdomen separate
and gape at the least touch. Remove the hairs and you shall see
that the skin, which was white, has turned brown and is changing to
black. Corruption is quickly doing its work.
This would be a good opportunity to speak of bacteria and cultures.
I shall do nothing of the sort. On the hazy borderland of the
visible and the invisible, the microscope inspires me with
suspicion. It so easily replaces the eye of reality by the eye of
imagination; it is so ready to oblige the theorists with just what
they want to see. Besides, supposing the microbe to be found, if
that were possible, the question would be changed, not solved. For
the problem of the collapse of the structure through the fact of a
prick there would be substituted another no less obscure: how does
the said microbe bring about that collapse? In what way does it go
to work? Where lies its power?
Then what explanation shall I give of the facts which I have just
set forth? Why, none, absolutely none, seeing that I do not know
of any. As I am unable to do better, I will confine myself to a
pair of comparisons or images, which may serve as a brief resting
place for the mind on the dark billows of the unknown.
All of us, as children, have amused ourselves with the game of
"card friars." A number of cards, as many as possible, are bent
lengthwise into a semi-cylinder. They are placed on a table, one
behind the other, in a winding row, the spaces in which are
suitably disposed. The performance pleases the eye by its curved
lines and its regular arrangement. It possesses order, which is a
condition of all animated matter. You give a little tap to the
first card. It falls and overturns the second, which, in the same
way, topsy-turvies the third; and so on, right to the end of the
row. In less than no time, the capsizing wave spreads and the
handsome edifice is shattered. Order is succeeded by disorder, I
might almost say, by death. What was needed thus to upset the
procession of friars? A very, very slight first push, out of all
proportion to the toppled mass.
Again, take a glass balloon containing a solution of alum
supersaturated by heat. It is closed, during the process of
boiling, with a cork and is then allowed to cool. The contents
remain fluid and limpid for an indefinite period. Mobility is here
represented by a faint semblance of life. Remove the cork and drop
in a solid particle of alum, however infinitesimal. Suddenly, the
liquid thickens into a solid lump and gives off heat. What has
happened? This: crystallization has set in at the first contact of
the particle of alum, the center of attraction; next, it has spread
bit by bit, each solidified particle producing the solidification
of those around. The impulse comes from an atom; the mass impelled
is boundless. The very small has revolutionized the immense.
Of course, in the comparison between these two instances and the
effects of my injections, the reader must see no more than a figure
of speech, which, without explaining anything, tries to throw a
glimmer of light upon it. The long procession of card friars is
knocked down by the mere touch of the little finger to the first;
the voluminous solution of alum suddenly turns solid under the
influence of an invisible particle. In the same way, the victims
of my operations succumb, thrown into convulsions by a tiny drop of
insignificant size and harmless appearance.
Then what is there in that terrible liquid? First of all, there is
water, inactive in itself and simply a vehicle of the active agent.
If a proof were needed of its innocuousness, here is one: I inject
into the thigh of any one of the sacred beetle's six legs a drop of
pure water larger than that of the fatal inoculations. As soon as
he is released, he makes off and trots about as nimbly as usual.
He is quite firm on his legs. When put back to his pellet, he
rolls it with the same zeal as before the experiment. My injection
of water makes no difference to him.
What else is there in the mixture in my watch glasses? There is
the disintegrated matter of the corpse, especially shreds of dried
muscles. Do these substances yield certain soluble elements to
water? Or are they simply reduced to a fine dust in the crushing?
I will not decide this question, nor is it really of importance.
The fact remains that the poison proceeds from those substances and
from them alone. Animal matter, therefore, which has ceased to
live is an agent of destruction within the organism. The dead cell
kills the living cell; in the delicate statics of life, it is the
grain of sand which, refusing its support, entails the collapse of
the whole edifice.
In this connection, we may recall those dreadful dissecting room
accidents. Through awkwardness, a student of anatomy pricks
himself with his scalpel in the course of his work; or else, by
inadvertence, he has an insignificant scratch on his hand. A cut
which one would hardly notice, produced by the point of a pocket
knife, a scratch of no account, from a thorn or otherwise, now
becomes a mortal wound, if powerful antiseptics do not speedily
remedy the ill. The scalpel is soiled by its contact with the
flesh of the corpse; so are the hands. That is quite enough. The
virus of corruption is introduced; and, if not treated in time, the
wound proves fatal. The dead has killed the living. This also
reminds us of the so-called carbuncle flies, the lancet of whose
mouth parts, contaminated with the sanies of corpses, produces such
My dealings as against insects are, when all is said, nothing but
dissecting room wounds and carbuncle flies' stings. In addition to
the gangrene that soon impairs and blackens the tissues, I obtain
convulsions similar to those produced by the scorpion's sting. In
its convulsive effects, the venomous fluid emitted by the sting
bears a close resemblance to the muscular infusions with which I
fill my injector. We are entitled, therefore, to ask ourselves if
poisons, generally speaking, are not themselves a produce of
demolition, a casting of the organism perpetually renewed, waste
matter, in short, which, instead of being gradually expelled, is
stored for purposes of attack and defense. The animal, in that
case, would arm itself with its own refuse in the same way as it
sometimes builds itself a home with its intestinal recrement.
Nothing is wasted; life's detritus is used for self defense.
All things considered, my preparations are meat extracts. If I
replace the flesh of the insect by that of another animal, the ox,
for instance, shall I obtain the same results? Logic says yes; and
logic is right. I dilute with a few drops of water a little
Liebig's extract, that precious standby of the kitchen. I operate
with this fluid on six Cetoniae or rosechafers, four in the grub
stage, two in the adult stage. At first, the patients move about
as usual. Next day, the two Cetoniae are dead. The larvae resist
longer and do not die until the second day. All show the same
relaxed muscles, the same blackened flesh, signs of putrefaction.
It is probable, therefore, that, if injected into our own veins,
the same fluid would likewise prove fatal. What is excellent in
the digestive tubes would be appalling in the arteries. What is
food in one case is poison in the other.
A Liebig's extract of a different kind, the broth in which the
liquefier puddles, is of a virulence equal, if not superior, to
that of my products. All those operated upon, Capricorns, sacred
beetles, ground beetles, die in convulsions. This brings us back,
after a long way round, to our starting point, the maggot of the
flesh fly. Can the worm, constantly floundering in the sanies of a
carcass, be itself in danger of inoculation by that whereon it
grows fat? I dare not rely upon experiments conducted by myself:
my clumsy implements and my shaky hand make me fear that, with
subjects so small and delicate, I might inflict deep wounds which
of themselves would bring about death.
Fortunately, I have a collaborator of incomparable skill in the
parasitic Chalcidid. Let us apply to her. To introduce her germs,
she has perforated the maggot's paunch, has even done so several
times over. The holes are extremely small, but the poison all
around is excessively subtle and has thus been able, in certain
cases, to penetrate. Now what has happened? The pupae, all from
the same apparatus, are numerous. They can be divided into three
not very unequal classes, according to the results supplied. Some
give me the adult flesh fly, others the parasite. The rest, nearly
a third, give me nothing, neither this year nor next.
In the first two cases, things have taken their normal course: the
grub has developed into a fly, or else the parasite has devoured
the grub. In the third case, an accident has occurred. I open the
barren pupae. They are coated inside with a dark glaze, the
remains of the dead maggot converted into black rottenness. The
grub, therefore, has undergone inoculation by the virus through the
fine openings effected by the Chalcidid. The skin has had time to
harden into a shell; but it was too late, the tissues being already
There you see it: in its broth of putrefaction, the worm is exposed
to grave dangers. Now there is a need for maggots in this world,
for maggots many and voracious, to purge the soil as quickly as
possible of death's impurities. Linnaeus tells us that 'Tres
muscae consumunt cadaver equi aeque cito ac leo." [Three flies
consume the carcass of a horse as quickly as a lion could do it.]
There is no exaggeration about the statement. Yes, of a certainty,
the offspring of the flesh fly and the bluebottle are expeditious
workers. They swarm in a heap, always seeking, always snuffling
with their pointed mouths. In those tumultuous crowds, mutual
scratches would be inevitable if the worms, like the other flesh
eaters, possessed mandibles, jaws, clippers adapted for cutting,
tearing and chopping; and those scratches, poisoned by the dreadful
gruel lapping them, would all be fatal.
How are the worms protected in their horrible work yard? They do
not eat: they drink their fill; by means of a pepsin which they
disgorge, they first turn their foodstuffs into soup; they practice
a strange and exceptional art of feeding, wherein those dangerous
carving implements, the scalpels with their dissecting room perils,
are superfluous. Here ends, for the present, the little that I
know or suspect of the maggot, the sanitary inspector in the
service of the public health.