How do flies stick to the wall?

Flies can stick to walls due to the tiny hairs on their feet, called setae. These setae have small pads at their tips that secrete a sticky substance, allowing the flies to adhere to surfaces. The setae also have a unique structure that allows them to be pulled in and out, increasing the fly's grip on the wall. Additionally, the hairs are covered in tiny hooks, which help to anchor the fly to the surface.