We call the foot pad a pulvillus.
Some insects do not have sticky hairs on the pulvillus.
There are beetles that simply put the pulvillus so flat against a smooth surface that it stays there by the pressure of the air above.
Some people think that is the way the pulvillus on the fly's foot acts.
Perhaps it acts both ways, sucking fast and sticking by hairs.
John wants to know if the beetle's pulvillus does not act just like the "sucker" that boys make.
The sucker, you know, is a round piece of leather with a string attached to the middle.
When the leather is wet and laid flat on the floor or on a smooth stone, all the air below it is pushed out, and the air above presses so hard that a boy cannot pull the leather up from the floor.
You can peel it up from one edge and let the air under easily enough, and then a baby could lift it.