Ants don't have lungs and breathe through tiny holes on the sides of their bodies.

Ants use a unique setup called a tracheal system to get oxygen. Instead of a nose or mouth, they have small valves called spiracles along their abdomen and thorax. The ant can open and close these valves to let air in or keep water out so they don't dry up.Once air enters a spiracle, it travels through a network of tubes called tracheae. These tubes branch out into even smaller paths called tracheoles. These tiny paths are so small that they reach almost every single cell in the ant's body. Oxygen simply moves through these tubes and into the cells naturally.This system works great for small creatures, but it has a major limit. It relies on a process called diffusion, where gas moves from where there is a lot of it to where there is less. This only works over very short distances. This is the main reason why ants stay small today.About 300 million years ago, during the Carboniferous period, the Earth's air was different. Oxygen levels were at 35% instead of the 21% we have now. Because there was so much more oxygen, it could travel further through these tubes. This allowed ancient insects to grow to giant sizes, like dragonflies with wings as wide as a hawk's wingspan.