FLIERS WITH WINGS OF GAUZE
Questioned as to the means to be adopted in order to protect from their
insect enemies the various plants he had mentioned in his last talk,
Uncle Paul was forced to acknowledge the inadequacy of any preventive
measures at our command.
“For protecting a few square yards of cabbage-patch from these
devourers,” he explained, “a rigorous search for worms and an incessant
chase after butterflies on that particular piece of land might prove
effective; but how keep watch over acres and acres, with butterflies
and moths of many kinds flying all about and alighting every moment to
lay their eggs? The cost of any such watchfulness would far exceed the
value of the crop. And so it is in general, with all raising of farm
products on a large scale: when once the enemy is in possession it is
all but impossible to drive him out if we depend on our own resources,
however much we may spend in the attempt. Because of their infinite
numbers the insects always have the advantage of us. But fortunately
there are others fighting for us, and they wage valiant warfare against
our insect foes, especially against worms and caterpillars.”
“You mean the birds?” asked Jules.
“Yes, and other equally useful helpers that you have never heard of,
notwithstanding the immense service they render us. I refer to the
insects belonging to the order known as hymenoptera.”
“Hymenoptera? I’ve never heard that word before.”
“And for that reason I hasten to explain its meaning to you. You are
familiar with the honey-bee, the bumblebee, and the wasp. Like
butterflies, they have four wings for flying; but these wings, instead
of being covered with scales—those scales that come off on your hand
and look like dust—are simply membranes of a transparent or gauzy
appearance. Hence the name hymenoptera that is given to these insects,
a Latin name that may be translated as ‘membranous-winged creatures.’
Furthermore, they have at the end of the abdomen a very fine sting
which comes out of its sheath when the irritated insect seeks to defend
itself by pricking the venturesome fingers that have seized it. In
other species this sting is represented sometimes by a kind of saw or
cutlass, sometimes by a blade, more or less long and slender, hidden in
a fold of the stomach or else projecting and open to view. Well,
insects thus armed with a sting, a saw, or a blade, and having four
membranous wings as fine and transparent as those of the honey-bee, the
bumblebee, and the wasp, are called hymenoptera. They form an order
just as butterflies and moths form the order of lepidoptera, and
insects with sheaths protecting the lower pair of wings form the order
of coleoptera.”
“The grasshopper,” Jules observed, “has a kind of sword on the end of
its body, but it hasn’t the bee’s fine, transparent wings.”
“Therefore it is not one of the hymenoptera.”
“The grasshopper doesn’t hurt any one with its sword, does it?” asked
Emile.
“No; it uses this tool simply for placing its eggs in the ground where
they are to hatch. It is a sort of conveyor for the eggs, and is called
a terebra. The saw, the blade, the cutlass, and other like implements
that terminate the body of various insects have also this name. They
serve to deposit the eggs in suitable places where the larvæ can find
food. But this implement, dangerous though it looks, never stings when
the insect is molested; it is not a defensive weapon. Only the
honey-bee, the bumblebee, the wasp, and some others have for their
defense a sting that inflicts a painful wound.”
“So painful,” Emile interrupted, “that I still remember how once, when
I wanted to see what was going on in the beehive, I was stung by the
bees.”
“The wasp’s sting is much worse,” remarked Louis. “When I was gathering
the grapes last year I took hold of a bunch where there were some
wasps, and my hand was swollen all day and pained me so I should have
cried if there had been nobody around.”
“How wonderful that such small creatures really hurt like that!” Jules
exclaimed. “I should like to know why.”
“I will tell you. The sting of these insects is a slender lancet, hard
and sharp-pointed, a kind of dagger finer than the finest needle. It is
situated at the end of the abdomen. In repose it is not seen, being
concealed in a sort of scabbard let into the creature’s body; but in
time of danger it comes out of this scabbard. Now, it is not exactly
the wound made by the sting that causes the smarting pain you know so
well. This wound is so slight, so subtle, that we cannot see it, and we
should hardly feel it if it were made by a needle or a thorn as fine as
the sting. But the sting communicates with a venom-sac lodged in the
insect’s body, and through a tiny channel running the length of the
sting there is injected into the very heart of the wound a minute
quantity of a highly dangerous liquid. After this injection the sting
is withdrawn, while the venom remains in the wound; and that is what
causes the pain.
“Learned men who have studied this curious subject relate the following
experiment, which was performed in order to prove that it is the
venomous liquid introduced into the wound, and not the wound itself,
that causes the pain. When one pricks oneself with a very fine needle
the pain is of no consequence and passes almost immediately. Well, the
prick of a needle, insignificant in itself, can be made very painful
indeed if the little wound is poisoned with venom from a bee or a wasp.
The learned men I just spoke of dipped the point of a needle into the
bee’s venom-sac and with the needle thus moistened lightly pricked
themselves. The pain that followed was severe and protracted, even
severer and of longer duration than if the insect itself had stung the
experimenters. This difference is to be explained by the fact that the
needle, large in comparison with the insect’s sting, introduced into
the wound much more venom than the sting itself could have conveyed.
Now you understand, I hope, that it is the injection of the venom into
the wound that causes all the mischief.”
“That is plain enough,” assented Jules.
“The bee’s sting is barbed,” continued Uncle Paul; “that is to say, it
is furnished with teeth somewhat like those of a saw and pointing
backward. In its haste to fly away after stinging, the bee does not
always succeed, on account of these teeth, in drawing out the sting
from the wound it has inflicted; and thus the sting is wrenched from
the bee’s body, to the endangering of the insect’s life. The venom-sac
is left behind also; it is that little white globule one sees outside
the wound and at the base of the sting. If the person stung, hastening
to extract the sting, is awkward enough to press on the little sac, a
great part of the venom is likely to be injected into the wound, with a
corresponding increase of pain. This is a warning to you, whenever you
are stung by a bee, to draw out the sting cautiously and to be careful
not to press on the venom-sac.”