_Uncle Philip tells the Boys about an Insect with Tweezers,
and another with Pincers; and shows them how a Fly's Foot is made,
so as to stick to the Wall._
"How do you do, Uncle Philip, this morning?"
"Very well, boys, I thank you. You are all well, I suppose, or I should
not see you here."
"Yes, we are all well, thank you, Uncle Philip. But one of us would be
very glad to have your help."
"Why, what is the matter?"
"Charles Walker has run a splinter into his hand, and he wishes you to
get it out for him."
"Oh, certainly, I will do that, if I can. Let me see: but stay--I must
first put on my spectacles. Ah, now I see it; I can get it out, but I
must take my tweezers to it. There, it is out."
"Uncle Philip, those tweezers are very useful. If you had not had them,
you could not have taken hold of the splinter with your fingers; and
what would you have done then?"
"Tried to cut it out with the point of my penknife; but the tweezers are
better for such work; and that reminds me, boys, to tell you that there
are insects with tweezers."
"Why, what tool is it that you cannot find among them, Uncle Philip? It
really seems as if you found almost every kind among the lower animals."
"Oh, no--no, boys. There are a great many which I cannot find; but there
are several, too, which, as you know, we have discovered."
"And, Uncle Philip, we suppose that men learned to make their tools and
work at many of their trades from these dumb creatures."
"Stay, boys--I never said that, because I think that it is not true. We
know that in some things men did not learn from the insects, though they
might have done so. There is paper, for instance. How could men learn
to make it from the wasps, when it was a thins: in common use a long
time before Mr. Reaumur, of whom I told you, found out how the wasp made
it? So, too, with a great many tools; men invented them, and afterward,
perhaps, it was found out that insects had instruments like them:
and at other times the insects did show men how to make some things.
I will tell you of one which I think of just now. The city of London,
in England, is on the river Thames. Some time since a plan was adopted
to make what is called a tunnel under the river. This tunnel is a road
dug out of the earth, under the bottom of the river, across it; and of
course to keep the water from pressing in the earth as fast as it was
hollowed out, it was propped up by walls built on each side, with a very
strong arch at the top. The work has now stopped; but about half of it
was made. In building this arched road under the water, the workmen used
what they called a shield, to keep the water from coming through upon
them: and the gentleman who invented it, says that he first thought of
it, from examining a little animal named Taret, which will bore holes in
large pieces of timber under the water. This little animal has upon its
head a kind of shield, by which it keeps off the force of the water, and
works without being disturbed. So here was a case in which the insect
taught the man."
"Uncle Philip, that gentleman was a sensible man, in the first place to
watch the Taret and examine its head, and in the next place not to be
too proud to learn from it. I expect he was a naturalist; was he, Uncle
Philip?"
"I do not know, boys; but I should think his discovery of the shield
would make him an attentive observer, if he was not so before."
"Now, Uncle Philip, will you tell us of the tweezers?"
"Very willingly, boys. This instrument or tool belongs to the moths
which you see flying about at times. The tails are covered with a down,
which grows in the form of a thick brush or tuft, and has a shining
silky gloss, different in colour from the short hair upon the rest
of the body. The moth pulls off this hair to cover its eggs, and the
tweezers are used for that purpose. Here is a picture of the moths."
[Illustration: Females of the brown and gold-tailed Moths, showing the
bunch of down on the tails.]
"Uncle Philip, you said that the moth pulled this hair off to cover its
eggs; are they easily frozen?"
"Not very easily, boys; but you are mistaken in thinking that the moth
covers these eggs to keep off the cold; for as she lays them in July and
August, and covers them at that time, it cannot be to keep off the cold."
"What is it for, then, Uncle Philip?"
"To keep off the summer heat, boys."
"Why, Uncle Philip! who ever heard of covering a thing up in hair or
wool to keep off heat?"
"I have heard of it, and seen it too, boys. It may seem strange, but
it is true, that down and wool, and such things, are nearly as good to
protect an animal from very great outward heat as they are to keep off
very severe cold. When I was at Naples, in Italy, it was summer;--the
climate is a very warm one.--The country people were in the habit of
bringing snow into the city from Mount Vesuvius, and every morning I
could see them coming in with their snow, which they sell to the rich
to use for cooling things: and they kept it from melting with straw
and wool. And in our own country, especially at the south, it is very
common when a large lump of ice is brought to the house to be used
through the day in midsummer, to wrap it up in a thick blanket until it
is wanted.
"But I have not yet told you of the tweezers. The moth has no jaws, like
bees and wasps, so that it cannot pull off these hairs as the bee would;
but, as I told you, it performs the work with its tweezers, which are
placed in its tail, and are like the points of a pair of sugar-tongs.
The insects, too, will use them very rapidly, and pull off a little of
the down, spread the egg upon it, and then cover it with more down, and
smooth it very neatly. Here are pictures of these tweezers."
[Illustration: Tweezers of the brown and gold-tailed Moths, magnified.]
"This is a curious instrument for the insect to have, Uncle Philip."
"True, boys, but a very useful one. I will tell you, however, of another
strange thing concerning moths with their tweezers; I mean the way
in which they will sometimes place their eggs. The kind of moth that
does this work is not exactly known, but naturalists think that the
eggs are moth's eggs, because they are covered with the down, exactly
like those which are known to be moth's eggs. These eggs are twisted
round a branch, like the thread of a screw, or like the curled end of
a corkscrew put over a small stick. Here is a picture of some of these
eggs."
[Illustration: Spiral group of Eggs of an unknown Moth.]
"Ah, this is wonderful work indeed for a moth, Uncle Philip."
"As you seem to like this, boys, I will just mention to you that there
is another moth, called the lackey-moth, which winds its eggs also
around a branch. They are hard, however, and not covered with any down,
and are put on in the strongest possible way. If men wish to make an
arch of stone, you know that the stones will be more narrow at the
bottom than at the top, so that the bottom of the arch may make a small
circle, and the top a larger one: thus--
[Illustration: A, Key-stone of an arch; B, Arch completed.]
Now the moth goes on this principle. Its eggs are shaped like the bowl
of a wine-glass, and the smaller end is put next to the branch. They are
all glued together, too, with a kind of gum, which will not dissolve or
melt in water; so that the rain cannot injure them. Here is a picture of
these eggs.
[Illustration: Eggs of the Lackey-moth, wound spirally round a twig of
hawthorn; natural size, and magnified.]
"There is another insect, boys, which has something like tweezers;
though I think they resemble pincers most."
"What is it, Uncle Philip?"
"The boys call it father long-legs, and I dare say you have often seen
it. It is the crane-fly, and its pincers are used for putting its egg in
the hole it has made for it."
"Where does it put its eggs, Uncle Philip?"
[Illustration: Ovipositor and Eggs of the Crane-fly.]
"In the earth, boys; and to enable the insect to do this, the female has
the pincers I spoke of: they are made of something like horn, and are
sharp at the point. With these she first bores a hole in the ground, and
then puts the egg in. The egg is like a grain of gunpowder, and she puts
herself in a very curious posture to bore the hole. Here, boys, you may
see a picture of the pincers as they appear through a microscope, for
they are not near as large as the picture. And here is a drawing of one
boring."
[Illustration: Crane-fly ovipositing, and the larva beneath, in the
earth, feeding upon grass roots.]
"What good pincers those are, Uncle Philip: but will you tell us one
thing which we wish to know? Talking about the crane-fly has put me in
mind of it: the other day we were sitting together in school, and the
wall over our heads was covered with common flies; and when we came out,
we were talking about the way in which the fly stuck to the wall without
falling down; and as we could not tell what kept him up, we agreed to
ask you about it."
"I will tell you, boys, very willingly. I do not wonder that you were
unable to tell how the fly stuck to the wall; for you never tried to
find out, and therefore could only guess at it."
"And that is not a good way to find out any thing, Uncle Philip?"
"No, boys; though some persons much older than you are, did nothing but
guess about this very thing, and guessed very far from the truth too.
Some thought that the fly had a sponge in its foot, and squeezed a sort
of glue out of it which made it stick fast; others said that the glass
or wall was so rough that the fly's feet would catch hold of the little
points upon it; but both were wrong."
"How does it hold on, Uncle Philip?"
"Did you ever see what the boys call a sucker, made of a piece of soft
sole leather? That will show you how the fly's foot sticks fast. This
leather is cut round, and has a string through the centre; the boys wet
it, and then put it upon a board or something smooth, and stamp on it,
and try to raise it up from the board by the string; and it requires
some strength to pull it up: sometimes they put it on a small smooth
stone, and then lift up the stone by it. The reason why the leather
sticks so fast is because the air is pressing on it upon the outside,
and there is very little or no air between it and the board, to press
the other way."
"Why, Uncle Philip, is the air heavy?"
"Oh yes, boys, when there is so much of it as there is above the earth,
it presses down very heavily. Now the fly's foot is like the sucker;
when he puts it down he has a contrivance to drive out the air from
under it, so that there will be little or none between it and the wall;
and then the outer air presses upon it, and holds it fast."
"But, Uncle Philip, how does he get it up again?"
"Why, boys, by another contrivance, he can let air in under his foot
again, and then he can easily move it; for we do not feel the weight of
air when it presses upon both sides of us. The reason why you stand up
straight is because the air is pressing all around you; if it were on
one side of you only, it would press you down on the other side. Here is
a picture of the fly's foot, as it appears through the microscope. You
will see it has three suckers with the edges all like saws; these are
to make it stick the closer. This picture, boys, is sixty-four hundred
times as large as the fly's foot is."
[Illustration: Fly's foot magnified.]
"But, Uncle Philip, there is one thing yet hard to understand."
"What is it?"
"Why, the fly walks on the wall over our heads; now the air cannot press
down upon his feet there."
"Very true, boys: it cannot press _down_, but it can and does press
_up_ against his feet; for the air presses up and down and sidewise all
alike."
"Ah, now it is plain enough, and we are much obliged to you, Uncle
Philip, for telling us what we wished to know."
"You are quite welcome, my dear boys, to all that I can teach you: if it
makes you to be wiser and better men when you grow up, I shall be very
thankful to God that I have been able to do you any good."
"Good morning, Uncle Philip."
"Good day, boys; I shall expect to see you all in church to-morrow."
"We shall be there, Uncle Philip."