THE CABBAGE-CATERPILLAR
The cabbage is the oldest vegetable we possess. We know that people in
classic times ate it, but it goes much further back than that, so that
indeed we are ignorant of when or how mankind first began cultivating
it. The botanists tell us that originally it was a long-stalked,
scanty-leaved, ill-smelling wild plant which grew on ocean cliffs.
History pays but little attention to such details: it celebrates the
battlefields on which we meet our death, it thinks the plowed fields by
which we thrive are not important enough to speak of; it can tell us
the names of kings’ favorites, it cannot tell us of the beginning of
wheat! Perhaps some day it will be written differently.
It is too bad that we do not know more about the cabbage, for it
would have some very interesting things to teach us. It is certainly
a treasure in itself. Other creatures think so besides man; and one
of these is the Caterpillar of the common Large White Butterfly.
This Caterpillar feeds on the leaves of the cabbage and all kinds of
cabbagey plants, such as the cauliflower, the Brussels sprout, the
kohlrabi, and the rutabaga, all near relatives of the cabbage.
It will feed also on other plants which belong to the cabbage family.
They are all of the order of the Cruciferæ, so-called by the botanists
because the petals are four in number and arranged in a cross. The
White Butterfly lays her eggs only on this order of plants. How she
knows them is a mystery. I have studied flowers and plants for fifty
years and more, yet, if I wished to find out if a plant new to me was
or was not one of the Cruciferæ, and there were no flowers or fruit to
guide me, I should believe the White Butterfly’s record on the matter
sooner than anything I could find in books.
The White Butterfly has two families a year: one in April and May, the
other in September. This is just the time that cabbages are ripe in our
part of the world. The Butterfly’s calendar agrees with the gardener’s.
When there are provisions to be eaten, the Caterpillars are on hand.
[Illustration]
The eggs are a bright orange-yellow and are laid in slabs, sometimes
on the upper surface, sometimes on the lower surface of the leaves.
The Caterpillars come out of their eggs in about a week, and the
first thing they do is to eat the egg-shells, or egg-wrappers, before
tackling the green leaves. It is the first time I have ever seen the
grub make a meal of the sack in which it was born, and I wonder what
reason it has. I suspect as follows: the leaves of the cabbage are
waxed and slippery. To walk on them without falling off, the grub needs
bits of silk, something for its legs to grip. To make this silk, it
needs special food; so it eats the egg-wrapper, which is of a horny
substance of the same nature as silk, and probably easily changed to
the latter in the stomach of the little grub.
[Illustration]
Soon the grubs get hungry for green food, and then the ruin of the
cabbages commences. What appetites they have! I served up to a herd
of these Caterpillars which I had in my laboratory a bunch of leaves
picked from among the biggest cabbages: two hours later nothing was
left but the thick middle veins. At this rate the cabbage bed will not
last long.
The gluttonous Caterpillars do nothing at all but eat, unless we except
a curious motion they sometimes indulge in. When several Caterpillars
are grazing side by side, you sometimes see all the heads in the row
briskly lifted and as briskly lowered, time after time, all together
and as accurately as if they were Prussian soldiers drilling. I do
not know whether this is their way of showing that they would fight,
if necessary, or a sign of pleasure in the eating and the warm sun.
Anyhow, it is the only exercise they take until they are full-grown and
fat.
After a whole month of grazing, the Caterpillars at last have enough.
They begin to climb in every direction. They walk about anyhow, with
the front part of their bodies raised and searching space. It is now
the beginning of cold weather, and my Caterpillar guests are in a small
greenhouse. I leave the door of the house open. Soon the whole crowd
have disappeared.
I find them scattered all over the neighboring walls, some thirty yards
off. They are under ledges and eaves, which will serve them as shelters
through the winter. The Cabbage-caterpillar is hardy and does not mind
the cold.
In these shelters they weave themselves hammock cocoons and turn into
chrysales, from which next spring the Moths will come.
[Illustration]
We may be interested in the story of the Cabbage-caterpillar, but
we know that there would be not enough cabbages for us if he were
allowed full sway. So we are not ill-pleased to hear that there is
still another insect who preys upon him and keeps him from being too
numerous. If the Cabbage-caterpillar is our enemy, this insect is our
friend. Yet she is so small, she works so discreetly, that the gardener
does not know her, has not even heard of her. If he were to see her by
accident, flitting around the plant which she protects, he would take
no notice of her, would not dream of the help she is giving him. I am
going to give the tiny midget her deserts.
[Illustration]
Scientists call her by a name as long as she is tiny. Part of the name
is Microgaster. It is what I shall have to call her, for she has no
other that I know of. You must blame the wise scientists who named her
that, and not me.
How does she work? Well, we shall see. In the spring, let us look about
our kitchen-gardens. We can hardly help noticing against the walls
or on the withered grasses at the foot of the hedges some very small
yellow cocoons, heaped into masses the size of a hazel-nut. Beside each
group lies a Cabbage-caterpillar, sometimes dead and always looking
very tattered. These cocoons are the work of the Microgaster’s family,
hatched or on the point of hatching; they have been feeding on the poor
Caterpillar.
The little Microgaster or Midge is about the size of a Gnat. When the
Caterpillar-moth lays her orange eggs on the cabbage leaves, the Midge
hastens up and with a slender, horny prickle she possesses, lays her
egg _inside_ the film of the Moth’s egg. Often many Midges lay their
little eggs in the same Moth’s egg. Judging by the cocoons, there are
sometimes as many as sixty-five Midges to one Caterpillar.
As the Caterpillar grows up, it does not seem to suffer; it feeds on
the cabbage leaves and, when that is done, makes its pilgrimage as
usual to find the place where it will weave its cocoon. It even begins
this work; but it is listless, it has no strength; it grows thin and
dies. No wonder, with a host of worms of the little Microgaster in its
body, drinking its blood! The Caterpillar has obligingly lived till
just the time when the Microgaster’s worms are ready to come out. They
do so, and begin to weave their cocoons, where they turn into Midges
with the long name.
[Illustration]