If you look at one of the cockroach's antennæ under the magnifying
glass, you will see it is made up of a good many short pieces, or
segments, as we call them, fastened together end to end.
Yes, Mollie, that is why it can move about so easily. It can curl up
like a whiplash, you see.
Next the head is a round segment that fits into a socket.
[Illustration]
Double up your right fist and fit it into the half-closed palm of your
left hand.
There! That is like the ball-and-socket joint.
You see you can move your fist around in all directions.
The insect can move its antennæ in all directions because they are
fastened to its head by ball-and-socket joints.
On the segments of the antennæ, particularly towards the tip, are little
dots.
You cannot see the dots without the help of a strong microscope, but
they are there.
These little dots are sensitive spots. There is a nerve coming from the
insect's brain to each dot.
Some of the dots are sensitive to odors, just as the nerves of our nose
are sensitive to odors.
May thinks it is very funny that the insects smell with antennæ instead
of with noses.
The insects, no doubt, would think it very funny for us to smell with,
noses instead of with antennæ, if they thought about it at all.
The little dots on the antennæ are extremely sensitive to smells. They
are often much more sensitive than our noses.
Put a bit of food at some distance from a hungry cockroach, and it will
not be long before a pair of long, sensitive feelers will come waving to
and fro out of some dark corner.
[Illustration]
Little Mrs. Cockroach has smelled the dainty morsel, and, as soon as it
is dark, out she will run, her feelers moving eagerly this way and that,
until she has found it.
Yes, May, insects also feel with their antennæ. That is why the antennæ
are often called "feelers."
There are other dots on the segments that are sensitive to touch.
Sometimes there are tiny hairs on the antennæ, also sensitive to touch.
The little fellows feel and smell, yes, and oftentimes _hear_ with their
antennæ.
Many insects have spots sensitive to sound on the antennæ.
Yes, indeed, May, it is wonderful that such tiny threads as an insect's
antennæ should hold so many kinds of sensitive spots.
An insect's antennæ are among the most wonderful things in the world.
And _I_ think a cockroach, in spite of its bad reputation, is a very
wonderful little fellow.
What is that, May? Our cockroach is drawing one of its antennæ through
its mouth?
Ah, yes, see it clean its antenna, children.
It seems to nibble at it as it draws it through its mouth.
Insects are very careful to keep their antennæ clean.
It would not do to let these sensitive spots become covered with dust,
you know.
[Illustration]