What can he be called, this creature whose style and title I dare not
inscribe at the head of the chapter? His name is Monodontomerus cupreus,
SM. Just try it, for fun: Mo-no-don-to-me-rus. What a gorgeous mouthful!
What an idea it gives one of some beast of the Apocalypse! We think,
when we pronounce the word, of the prehistoric monsters: the mastodon,
the mammoth, the ponderous megatherium. Well, we are misled by the
scientific label: we have to do with a very paltry insect, smaller than
the common gnat.
There are good people like that, only too happy to serve science with
resounding appellations that might come from Timbuktu; they cannot name
you a midge without striking terror into you. O ye wise and revered
ones, ye christeners of animals, I am willing, in my study, to
make use--but not undue use--of your harsh terminology, with its
conglomeration of syllables; but there is a danger of their leaving the
sanctum and appearing before the public, which is always ready to show
its lack of deference for terms that do not respect its ears. I, wishing
to speak like everybody else, so that I may be understood by all, and
persuaded that science has no need of this Brobdignagian jargon, make a
point of avoiding technical nomenclature when it becomes too barbarous,
when it threatens to lumber the page the moment my pen attempts it. And
so I abandon Monodontomerus.
It is a puny little insect, almost as tiny as the midges whom we see
eddying in a ray of sunshine at the end of autumn. Its dress is golden
bronze; its eyes are coral red. It carries a naked sword, that is to
say, the sheath of its drill stands out slantwise at the tip of its
belly, instead of lying in a hollow groove along the back, as it
does with the Leucospis. This scabbard holds the latter half of the
inoculating filament, which extends below the animal to the base of
the abdomen. In short, its utensil is that of the Leucospis, with this
difference, that its lower half sticks out like a rapier.
This mite that bears a sword upon her rump is yet another persecutor of
the mason bees and not one of the least formidable. She exploits their
nests at the same time as the Leucospis. I see her, like the Leucospis,
slowly explore the ground with her antennae; I see her, like the
Leucospis, bravely drive her dagger into the stone wall. More taken up
with her work, less conscious perhaps of danger, she pays no heed to the
man who is observing her so closely. Where the Leucospis flies, she does
not budge. So great is her assurance that she comes right into my study,
to my work table, and disputes my ownership of the nests whose occupants
I am examining. She operates under my lens, she operates just beside
my forceps. What risk does she run? What can one do to a thing so very
small? She is so certain of her safety that I can take the Mason's
nest in my hand, move it, put it down and take it up again without
the insect's raising any objection: it continues its work even when my
magnifying glass is placed over it.
One of these heroines has come to inspect a nest of the Chalicodoma of
the Walls, most of whose cells are occupied by the numerous cocoons of
a parasite, the Stelis. The contents of these cells, which have been
partially ripped up to satisfy my curiosity, are very much exposed to
view. The windfall appears to be appreciated, for I see the dwarf ferret
about from cell to cell for four days on end, see her choose her cocoon
and insert her awl in the most approved fashion. I thus learn that
sight, although an indispensable guide in searching, does not decide
upon the proper spot for the operation. Here is an insect exploring not
the stony exterior of the mason's dwelling, but the surface of cocoons
woven of silk. The explorer has never found herself placed in such
circumstances, nor has any of her race before her, every cocoon, under
normal conditions, being protected by a surrounding wall. No matter:
despite the profound difference in the surfaces, the insect does not
waver. Warned by a special sense, an undecipherable riddle to ourselves,
it knows that the object of its search lies hidden under this unfamiliar
casing. The sense of smell has already been shown to be out of the
question; that of sight is now eliminated in its turn.
That she should bore through the cocoons of the Stelis, a parasite of
the mason bee, does not surprise me at all: I know how indifferent my
bold visitor is to the nature of the victuals destined for her family. I
have noticed her presence in the homes of bees differing greatly in
size and habits: Anthophorae, Osmiae, Chalicodomae, Anthidia. The Stelis
exploited on my table is one victim more; and that is all. The interest
does not lie there. The interest lies in the maneuvers of the insect,
which I am able to follow under the most favorable conditions.
Bent sharply at right angles, like a couple of broken matches, the
antennae feel the cocoon with their tips alone. The terminal joint is
the home of this strange sense which discerns from afar what no eye
sees, no scent distinguishes and no ear hears. If the point explored be
found suitable, the insect hoists itself on tiptoe so as to give full
scope to the play of its mechanism; it brings the tip of the belly
a little forward; and the entire ovipositor--inoculating-needle and
scabbard--stands perpendicular to the cocoon, in the center of the
quadrilateral described by the four hind legs, an eminently favorable
position for obtaining the maximum effect. For some time, the whole of
the awl bears on the cocoon, feeling all round with its point, groping
about; then, suddenly, the boring needle is released from its sheath,
which falls back along the body, while the needle strives to make its
entrance. The operation is a difficult one. I see the insect make a
score of attempts, one after the other, without succeeding in piercing
the tough wrapper of the Stelis. Should the instrument not penetrate,
it retreats into its sheath and the insect resumes its scrutiny of the
cocoon, sounding it point by point with the tips of its antennae. Then
further thrusts are tried until one succeeds.
The eggs are little spindles, white and gleaming like ivory, about
two-thirds of a millimeter in length. They have not the long, curved
peduncle of the Leucospis' eggs; they are not suspended from the
ceiling of the cocoon like these, but are laid without order around
the fostering larva. Lastly, in a single cell and with a single mother,
there is always more than one laying; and the number of eggs varies
considerably in each. The Leucospis, because of her great size, which
rivals that of her victim, the Bee, finds in each cell provisions enough
for one and one alone. When, therefore, there is more than one set of
eggs in any one cell, this is due to a mistake on her part and not a
premeditated result. Where the whole ration is required for the meals
of a single grub, she would take good care not to install several if
she could help it. Her competitor is not called upon to observe the
same discretion. A Chalicodoma grub gives the dwarf the wherewithal to
portion a score of her little ones, who will live in common and in all
comfort on what a single son of the giantess would eat up by himself.
The tiny boring engineer, therefore, always settles a numerous family
at the same banquet. The bowl, ample for a dozen or two, is emptied in
perfect harmony.
Curiosity made me count the brood, to see if the mother was able to
estimate the victuals and to proportion the number of guests to the
sumptuousness of the fare provided. My notes mention fifty-four larvae
in the cell of a masked Anthophora (Anthophora personata). No other
census attained this figure. Possibly, two different mothers had laid
their eggs in this crowded habitation. With the Mason bee of the Walls,
I see the number of larvae vary, in different cells, between four
and twenty-six; with the mason bee of the Sheds, between five and
thirty-six; with the three-horned Osmia, who supplied me with the
largest number of records, between seven and twenty-five; with the
blue Osmia (Osmia cyanea, KIRB.), between five and six; with the Stelis
(Stelis nasuta), between four and twelve.
The first return and the last two seem to point to some relation between
the abundance of provisions and the number of consumers. When the mother
comes upon the bountiful larva of the masked Anthophora, she gives it
half-a-hundred to feed; with the Stelis and the blue Osmia, niggardly
rations both, she contents herself with half-a-dozen. To introduce into
the dining room only the number of boarders that the bill of fare will
allow would certainly be a most deserving performance, especially as the
insect is placed under very difficult conditions to judge the contents
of the cell. These contents, which lie hidden under the ceiling, are
invisible; and the insect can derive its information only from the
outside of the nest, which varies in the different species. We
should therefore have to admit the existence of a particular power
of discrimination, a sort of discernment of the species, which is
recognized as large or small from the outward aspect of its house. I
refuse to go to this length in my conjectures, not that instinct seems
to me incapable of such feats, but because of the particulars obtained
from the three-horned Osmia and the two mason bees.
In the cells of these three species, I see the number of larvae put out
to nurse vary in so elastic a fashion that I must abandon all idea of
proportionate adjustment. The mother, without troubling unduly whether
there be an excess or a dearth of provisions for her family, has filled
the cells as her fancy prompted, or rather according to the number of
ripe ovules contained in her ovaries at the time of the laying. If food
be over-plentiful, the brood will be all the better for it and will grow
bigger and stronger; if food be scarce, the famished youngsters will not
die, but will remain smaller. Indeed, with both the larva and the full
grown insect, I have often observed a difference in size which varies
according to the density of the population, the members of a small
colony being double the size of their overcrowded neighbors.
The grubs are white, tapering at both ends, sharply segmented and
covered all over their bodies with a coat of fine, soft hairs which is
invisible except under the lens. The head consists of a little knob much
smaller in diameter than the body. In this head, the microscope reveals
mandibles consisting of fine spikes of a tawny red, which spread into a
wide, colorless base. Deprived of any indentation, incapable of chewing
anything between their awl-shaped ends, these two tools serve at best to
fix the grub slightly at some point of the fostering larva. Useless for
carving, therefore, the mouth is a pure osculatory sucker, which drains
the provisions by a process of exudation through the skin. We see here
repeated what the Anthrax and the Leucospis have already shown us:
the gradual exhaustion of a victim which the parasite consumes without
killing it.
It is a curious spectacle even after that of the Anthrax. We have here
twenty or thirty starvelings, all with their mouths pressed, as for a
kiss, to the body of the plump larva, which, from day to day, fades and
shrinks without the least appreciable wound, thus keeping fresh until
reduced to a shriveled slough. If I disturb the gluttonous swarm, all,
with a sudden recoil, let go, drop off and flounder around the foster
mother. They are no less prompt in resuming their savage kisses. I need
not add that neither at the point where they leave off nor at the point
where they recommence is there the faintest trace of liquid. The oily
exudation occurs only when the pump is at work. To linger over this
strange method of feeding is superfluous after what I have said about
the Anthrax.
The appearance of the full grown insect takes place at the beginning of
summer, after nearly a whole year's stay in the invaded dwelling. The
large number of inhabitants of one and the same cell led me to think
that the work of deliverance ought to present a certain interest. They
are all equally anxious to clear the walls of the prison at the earliest
possible moment and to come forth into the great festival of the sun: do
they all at the same time, in a confused horde, attack the ceiling which
has to be pierced? Is the work of deliverance arranged in the general
interest? Or is individual selfishness the only rule? These are the
questions which observation will answer.
A little in advance of the proper season, I transfer each family into
a short glass tube, which will represent the natal cell. A good, thick
cork, quite a centimeter deep, is the obstacle to be pierced for
an outlet. Well, instead of the mad haste and the ruinous lack of
organization which I expected to find, my broods show me in their glass
prison an exceedingly well regulated workshop. One insect, one only,
works at perforating the cork. Patiently, with its mandibles, grain by
grain, it digs a tunnel the width of its body. The gallery is so narrow
that, in order to return to the tube, the worker has to move backwards.
It is a slow process; and it takes hours and hours to dig the hole, a
hard job for the frail miner.
Should her fatigue become too great, the excavator leaves the forefront
and mingles with the crowd, to polish and dust herself. Another, the
first neighbor at hand, at once takes her place and is herself relieved
by a third when her task is done. Others again take their turn, always
one at a time, so much so that the works are never at a standstill
and never overcrowded. Meanwhile, the multitude keeps out of the way,
quietly and patiently. There is no anxiety as to the deliverance.
Success will come: of that they are all convinced. While waiting, one
washes her antennae by passing them through her mouth, another polishes
her wings with her hind legs, another frisks about to while away the
period of inaction. Some are making love, a sovran means of killing
time, whether one be born that day or twenty years ago.
Some, I said, make love. These favored ones are rare; they hardly count.
Is it through indifference? No, but the gallants are lacking. The sexes
are very unequally represented in the population of a cell: the males
are in a wretched minority and sometimes even completely absent. This
poverty did not escape the older observers. Brulle [Gaspard August
Brulle (1809-1873)], the author of many works on natural history and one
of the founders of the Societe entomologique de France, the only author
whom I am able to consult in my hermitage, says, literally: 'The males
do not appear to be known.'
I, for my part, know them; but, considering their feeble number, I keep
asking myself what part they play in a harem so disproportionate to
their forces. A few figures will show us what my hesitations are based
upon.
In twenty-two Osmia cocoons (Osmia tricornis), the total census of the
inmates yields three hundred and fifty-four, of whom forty-seven
are males and three hundred and seven females. The average number of
inmates, therefore, is sixteen individuals; and there are six females at
least to one male. This disparity is maintained, in more or less marked
proportions, whatever the species of the bee invaded. In the cocoons of
the Mason bee of the Sheds, I discover the average proportion to be six
females to one male; in those of the Mason bee of the Walls, I find one
male to fifteen females.
These facts, which I am unable to state with any greater precision, are
enough to give rise to the suspicion that the males, who are even tinier
dwarfs than the females and who, moreover, like all insects, are injured
by a single act of pairing, must, in most cases, remain strangers to
the females. Can the mothers, in fact, dispense with their assistance,
without being deprived of offspring on that account? I do not say yes,
but I do not say no. The duality of the sexes is a hard problem. Why
two sexes? Why not just one? It would have been much simpler and saved
a great deal of foolery. Why such a thing as sex, when the tuber of the
Jerusalem artichoke can do without it? These are the pregnant questions
suggested to me, in the end, by Monodontomerus cupreus, the insect so
infinitesimal in body and so overpowering in name that I had really
vowed never to speak of it again by its official designation.