A Formica ant

At the risk of sounding insulting, perhaps this isn't so much a matter of the ant being inherently indestructable as it is your hand and thumb being somewhat abnormally...shall we say...sponge-like?

thats why i said that this is an odd topic. all the replies seems like making fun. this was my observation so i shared. no problems will find elsewhere.

Your hand is soft and has plenty of movement due to the flesh, so is your thumb, the ant is hard. Now, due to both objects in contact with the ant being soft you are not able to exert enough point force on the ant to cause it harm. When you press really hard the ant just sinks into your skin and flesh but the amount of force exerted on the ant doesn't actually increase that much (because the force is actually compressing your flesh, not the harder ant).

Try with a peanut (or similar) in your hand, and then try applying the same force but with the peanut (or similar) between a hard surface. Now try between two hard surfaces.

See the difference the same force has when applied by soft and hard surfaces?

very convincing, thanks for taking/giving a serious thought on my odd experience.

Manas, You must understand that most people know them as wood or carpenter ants, not formica ants. Formica is a tradename of a phenolic based laminate, commonly used for countertops.

That is why people are giving you a hard time.

now to answer your question, it is because your thumb is far larger than the ant and the force is being directed around the ant by the pad of your thumb which was designed by nature to evenly spread out forces. since you cannot focus the force of your thumb on such a small area, the forces actually exerted on the ant are relatively small.

Have you ever tried to crush a flea with your hands?

I've tried dog- and cat-fleas, and never managed to do them any damage at all by squeezing between thumb and forefinger - even while rubbing at the same time. The little buggersbeasts just hop away. Needs at least one fingernail applied against thumb or finger with great force, and sometimes doesn't have much effect unless it's between two fingernails.

Surprising how effective a chitinous exoskeleton can be as armour for small creatures.

Siphonaptera (fleas) are remarkable creatures. Like some other insects, they have a ratchet-like mechanism which is used to "wind up" their resilin springs so they can leap such relatively huge distances.