Carefully.
As they weigh nearly nothing the effect of gravity is minimal.
You see the ceiling as smooth, flies see it as a very rough surface.
There are plenty of "handholds" for their feet with hooked claws at the end.
I have discovered that they have an Ovi Positor (think that's spelt right) in their rear which extends from the body and attaches to the surface and they deficate through this. It is also used for when they lay eggs. My father in law and I have been trying to discover this answer for ages.
they have super microfiber hair on the bottom and all around their legs to help them grip
No
Your head will be touching the ceiling
He painted the ceiling of the Sistine chapel.
no ship flies the American flag upside down when leaving port
hummingbird
It gobbles up!!
Lionel Ritchie: Dancing on the Ceiling
the artist who sings the upside down during 80's new wave is TWO MINDS CRACK.
The fly makes contact with the ceiling with its front legs. Using the momentum from flying, it swings the rest of its body and it's legs attach to the ceiling.
Spiders, ants, and flies can. I'm sure lots of others can, too.
No it has not yet, but you could possibly build it on your ceiling, but it would never work out the way you would plan as a regular toilet. (but technically a space toilet could work upside down)
Centipede
You've probably seen a fly scurrying across your ceiling. Although its body is totally upside down, it doesn't fall off. Flies have six legs attached to the thorax, or middle section, of their bodies. Each leg has a foot. On the underside of each foot are two tiny claws. Under each claw is a hairy pad called a pulvillus. These pads are covered in a sticky, glue-like liquid. When a fly walks on the ceiling or any other surface, the pads stick or clinglong enough forthe fly to keep its balance. Thislets flies walk upside down without falling off.