rder to see this hollow or groove, you must look on the under side
of the leg.

Yes, John, it reminds us of the ball-and-socket joint, only this is a
hinge joint, and does not move in so many directions.

The tibia can move towards the femur and away from it on this hinge.

When our little friend gets ready to jump, he draws the tibia close up
to the femur. When he jumps, he pushes the femur quickly away from the
tibia.

If you watch the grasshoppers, you will soon understand just how they
use their hind legs in jumping.

The tarsus bends easily.

It has three joints.

The last segment is a cunning little foot.

What is John doing?

He is looking at the grasshopper's foot through the magnifying glass.
Wise John!

Let us all look.

Yes, Charlie, we will try to draw it.

Mollie has hers drawn already. Do not hurry too much, Mollie. You cannot
draw well if you hurry.

See the sharp claw on each side of the foot.

[Illustration]

Let us mark these claws _a_ and _b_.

Between them is a flat little pad which we may as well mark _c_.

May says her picture looks like a crazy pond lily.

Let us see, May. Well, it _is_ rather funny.

If I were you, I should try again. Any child can learn to draw who will
keep trying.

Touch the grasshopper's foot with the tip of your finger.

How the little foot clings to you!

It clings by the two little claws that have caught in your skin, and
that hold fast.

[Illustration]

What do you suppose the little pad between the claws is for?

It is important, I can tell you.

John says he has heard there is a little pad in the fly's foot that
enables it to walk on glass.

Yes, and it is the same with the grasshopper.

The little pad between the claws is fringed with hairs.

You can see them with a good magnifying glass.

Out of the tip of each hair comes a little drop of sticky liquid.

This fastens the foot to any smooth surface.

Many insects have these sticky hairs on their foot pads.

When a fly walks up a window pane, it does it by gluing its feet, one
after the other, to the glass.

I don't wonder you laugh.

No, Mollie, the glue does not harden and hold it fast.

The fly can easily pull its foot loose. The grasshopper cannot walk on
glass quite as well as the fly. Its foot pads do not cling so well.

[Illustration]

Would you not like to know the name of these curious little foot pads?

We call the foot pad a _pulvillus_.

Some insects do