A NUMEROUS FAMILY
“A PLANT-LOUSE, we will suppose,” resumed Uncle Paul, “has just
established itself on the tender shoot of a rosebush. It is alone, all
alone. A few days after, young plant-lice surround it: they are its
sons. How many are there? Ten, twenty, a hundred? Let us say ten. Is
that enough to assure the preservation of the species? Don’t laugh at my
question. I know well that if the plant-lice were missing from the
rosebushes, the order of things would not be sensibly changed.”
“The ants would be the most to be pitied,” said Emile.
“The round earth would continue to turn just the same, even when the
last plant-louse was dying on its leaf; but it is not, in truth, an idle
question to ask if ten plant-lice suffice to preserve the race; for
science has no higher object than the quest of providential means for
maintaining everything in a just measure of prosperity.
“Well, ten plant-lice coming from one would be far too many if we did
not have to take account of destructive agencies. One replacing one, the
population remains the same; ten replacing one, in a short time the
number increases beyond all possible limits. Think of the dervish’s
grain of wheat doubled sixty-four times, so that it becomes a bed of
wheat of a finger’s depth over the whole earth. What would it be if it
had been multiplied ten times instead of doubled! In like manner, after
a few years, the descendants of a first plant-louse, continually
multiplied tenfold, would be in straitened circumstances in this world.
But there is the great reaper, death, which puts an invincible obstacle
to overcrowding, counterbalances life in its overgrowing fecundity, and,
in partnership with it, keeps all things in a perpetual youth. On a
rosebush apparently most peaceful there is death every minute. But the
small, the humble, and weak, are the habitual pasture, the daily bread,
of the large eaters. To how many dangers is not the plant-louse exposed,
so tiny, so weak, and without any means of defense! No sooner does a
little bird, hardly out of the shell, discover with its piercing eyes a
spot haunted by the plant-lice, than, merely as an appetizer, it will
swallow hundreds. And if a worm, far more rapacious, a horrible worm
expressly created and put into the world to eat you alive, joins in, ah!
my poor plant-lice, may God, the good God of little creatures, protect
you; for your race is indeed in peril.
“This devourer is of a delicate green with a white stripe on its back.
It is tapering in front, swollen at the back. When it doubles itself up
it takes the shape of a tear-drop. They call it the ants’ lion because
of the ravages it makes in the stupid herd. It establishes itself among
them. With its pointed mouth, it seizes one, the biggest, the plumpest;
it sucks it and throws away the skin, which is too hard for it. Its
pointed head is lowered again, a second plant-louse seized, raised from
the leaf, and sucked. Then another and another, a twentieth, a
hundredth. The foolish herd, whose ranks are thinning, do not even seem
to perceive what is going on. The trapped plant-louse kicks between the
lion’s fangs; the others, as if nothing were happening, continue to feed
peacefully. It would take a good deal more than that to spoil their
appetite! They eat while they are waiting to be eaten. The lion has had
enough. He squats amidst the herd to digest at his ease. But digestion
is soon over and already the greedy worm has its eye on those that he
will soon crunch. After two weeks of continual feasting, after having
browsed as it were on whole herds of plant-lice, the worm turns into an
elegant little dragon-fly with eyes as bright as gold, and known as the
_hemerobius_.
[Illustration: Ladybug (_a_) larva (_b_) pupa (_c_) first joint of
larva]
“Is that all? Oh, no. Here is the lady-bug, the good God’s bug. It is
round and red, with black spots. It is very pleasing; it has an innocent
air. Who would take it also to be a devourer, filling its stomach with
plant-lice? Look at it closely on the rosebush, and you will see it at
its ferocious feasting. It is very pretty and innocent-looking; but it
is a glutton, there is no denying the fact, so fond is it of plant-lice.
“Is that all? Oh, no. Those poor plant-lice are manna, the regular diet
of all sorts of ravagers. Young birds eat them, the _hemerobius_ eats
them, lady-birds eat them, gluttons of all kinds eat them; and still
there are always plant-lice. Ah! that is where, in the fight between
fecundity which repairs and the rough battle of life which destroys, the
weak excel by opposing legions and legions to the chances of
annihilation. In vain the devourers come from all sides and pounce upon
their prey; the devoured survive by sacrificing a million to preserve
one. The weaker they are, the more fruitful they are.
“The herring, cod, and sardine are given over as pasturage for the
devourers of the sea, earth, and sky. When they undertake long voyages
to graze in favorable spots, their extermination is imminent. The hungry
ones of the sea surround the school of fish; the famished ones of the
sky hover over their route; those of the earth await them on the shore.
Man hastens to lend a strong hand to the killing and to take his share
of the sea food. He equips fleets, goes to the fish with naval armies in
which all nations are represented; he dries in the sun, salts, smokes,
packs. But there is no perceptible diminution in the supply; for him the
weak are infinite in number. One cod lays nine million eggs! Where are
the devourers that will see the end of such a family?”
“Nine million eggs!” exclaimed Emile. “Is that a great many?”
“Just to count them, one by one, would take nearly a year of ten working
hours each day.”
“Whoever counted them had lots of patience,” was Emile’s comment.
“They are not counted,” replied Uncle Paul; “they are weighed, which is
quickly done; and from the weight the number is deduced.
“Like the cod in the sea, the plant-lice are exposed on their rosebushes
and alders to numerous chances of destruction. I have told you that they
are the daily bread of a multitude of eaters. So, to increase their
legions, they have rapid means that are not found in other insects.
Instead of laying eggs, very slow in developing, they bring forth living
plant-lice, which all, absolutely all, in two weeks have obtained their
growth and begin to produce another generation. This is repeated all
through the season, that is to say at least half the year, so that the
number of generations succeeding one another during this period cannot
be less than a dozen. Let us say that one plant-louse produces ten,
which is certainly below the actual number. Each of these ten plant-lice
borne by the first one bears ten more, making one hundred in all; each
of these hundred bears ten, in all one thousand; each of the thousand
bears ten, in all ten thousand; and so on, multiplying always by ten,
eleven times. Here is the same calculation as the dervish’s grain of
wheat, which grew with such astonishing rapidity when they multiplied it
by two. For the family of the plant-lice the increase is much more
rapid, as the multiplication is made by ten. It is true that the
calculation stops at the twelfth instead of going on to the
sixty-fourth. No matter, the result would stupefy you; it is equal to a
hundred thousand millions. To count a cod’s eggs, one by one, would take
nearly a year; to count the descendants of one plant-louse for six
months would take ten thousand years! Where are the devourers that would
see the end of the miserable louse? Guess how much space these
plant-lice would cover, as closely packed as they are on the elder
branch.”
“Perhaps as large a place as our garden,” suggested Claire.
“More than that; the garden is a hundred meters long and the same in
width. Well, the family of that one plant-louse would cover a surface
ten times larger; that is to say, ten hectares. What do you say to that?
Is it not necessary that the young birds, little lady-bugs, and the
dragon-fly with the golden eyes should work hard in the extermination of
the louse, which if unhindered would in a few years overrun the world?
“In spite of the hungry ones which devour them, the plant-lice seriously
alarm mankind. Winged plant-lice have been seen flying in clouds thick
enough to obscure the daylight. Their black legions went from one canton
to another, alighted on the fruit trees, and ravaged them. Ah! when God
wishes to try us, the elements are not always unchained. He sends
against us in our pride the paltriest of creatures. The invisible mower,
the feeble plant-louse, comes, and man is filled with fear; for the good
things of the earth are in great peril.
“Man, so powerful, can do nothing against these little creatures,
invincible in their multitude.”
Uncle Paul finished the story of the ants and their cows. Several times
since, Emile, Jules, and Claire have talked of the prodigious families
of the plant-louse and the cod, but rather lost themselves in the
millions and thousand millions. Their uncle was right: his stories
interested them much more than Mother Ambroisine’s tales.
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