Mikes Johnson, age 12, of Mt. Vernon, Washington, for his question:

How can a fly walk on the ceiling?

A fly looks much too small to take care of himself and keep out of trouble. If you think this, you discover your mistake when you try to swat the little nuisance. You may be very fast with the fly shatter, but almost always he is faster. Hs has many more amazing tricks, such as walking upside down on the ceiling:

You need more than the best eyesight to get a good look at the tiny fly. A good magnifying glass or a hand lens will reveal that he is far more than a fuzzy black dot with a pair of gauzy wings. You will see the pair of huge compound eyes which cover most of his head. You will see that his small body is covered with bristly hairs,

Even his spindly legs are covered with bristles: Each leg ends in a foot so small that you need a powerful microscope to study it. Even then, the little foot is so strange that you will find it hard to believe. Like everything else about him, it is very different from the feet we are used to seeing on cats, dogs, birds, bears and other sizeable animals.

The main part of each foot is a pair of claws curved like a new moon. At the base of each prong is a hairy pad and each pad is fed by glands which give off a sticky fluid. The fly has six of these amazing fast and each one is fitted with a pair of grappling hooks and two sticky pads.

It takes more than one thousand flies to weigh an ounce, This means that each fly is not very heavy and therefore he does not have to exert much strength to defy the pull of gravity. His little grappling hooks and sticky pads are strong enough to hold him when he stands on the side of a sheer cliff, They are even strong enough to hold him upside down on the ceiling.

But the little creature can do even more to defy the laws of gravity. He can actually walk upside down on the ceiling. The hairy pads on his feet are not sticky enough to glue him to the spots They ate just sticky enough to hold him and when he chooses he can lift them up and put them dawn again. This i s what happens when he walks on the ceiling. He steps along by pulling up three sticky feet and putting them clown.

The fly is a dangerous animal because he carries germs from place to place. Bacteria cling to has hair bristles and brush off an the next object he touches. And his greatest danger lies in those sticky feet. He hangs around garbage arid decaying material where germs are plentiful and all kinds of unwanted bacteria cling to his feet. If he then gets into the kitchen, some of these germs are left behind on the objects he uses to stand and walk upon.