system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Do Ants (and/or other similar insects) Breathe? Like breathe and respirate in a similar way to Humans/Mamals?
gpt
Most insects breathe through spiracles, which are tiny pores on their legs that allow air into their bodies. However, they do not have lungs or anything like that, largely because they also have no circulatory system. Instead of a heart pumping blood to a single central area to get oxygenated the way we work, insects have "open" circulation, where the heart just keeps a freely-flowing pool of blood-like substance flowing around all the organs. They have no blood vessels, and everything in their body cavities is more or less just floating in a soup of blood.

This works for insects specifically because they are tiny. Oxygen doesn't have to go as far to perfuse (or soak into) all of their tissues, so just having a free-flowing soup of blood running past some openings on the legs is just fine for them. The oxygen will get into their tissues because they have so little tissue which needs oxygenation. This is one of the hard limits on insect size, as if they get too large their tissues will get oxygen starved. This is also why insects were absolutely gigantic hundreds of millions of years ago, as oxygen levels were much higher at that time, so they could more easily perfuse a larger body.