How can Insects be Attached to Walls or Ceilings, Defying Gravity?

How can insects be attached to walls or ceilings? Have you ever wondered how insects can stick well to walls or even very smooth ceilings, like glass, defying the laws of gravity? They can even move without gravity. How is that possible? 

The first evidence supporting this idea lies in the structures of insects' legs. After a close examination, you will see the coxa, trochanter, femur, tibia, pastern joint, pretarsus, and palmula. If you focus on the pretarsus, you will see the palmula, claws, and fine bristles. Their feet are suitable for climbing rough surfaces, while insects with palmula-sticky mucus can stick to slippery surfaces. The shapes of these features may vary depending on the type of insect, but regardless, they enable insects to adapt and attach themselves to various environments. 

However, insects are not typically stationary; they move around and fly away. So, how do they smoothly adhere and detach? In this regard, research conducted at the University of Cambridge in the UK provides some insight. They discovered that insects secrete a thin, sticky liquid membrane through the palmula and conducted experiments to identify its composition. As a result, they found that the substance consists of nanometer-thick oil and water ingredients. This substance is a nonnewtonian fluid that can be changed to liquid or solid depending on how much force it receives. Without further ado, depending on the insects, there are some hairs, and some don't. 

However, the presence of hairs is not crucial for insect attachment. If you zoom in on the hair, there is fine bristle. When the non-Newton fluid is secreted and attached to the wall or ceiling, it solidifies and creates 100 to 300 times more powerful adhesion than its own weight, allowing it to remain attached to the wall or ceiling. To detach, the insects bend the pretarsus to concentrate strong stress. At this point, the fine droplets clustered together on the fine protrusion break off and become liquid again. These scientific reasons explain how insects can defy gravity.