How do insects breathe?

Microscopic observation revealed that insects breathe air through their mouths.

Oxygen is one of the most important molecules needed for growth and sustaining life. Humans and other mammals absorb oxygen through respiration. We breathe in and inhale oxygen into our lungs, which then disperses it to all tissues through the blood stream. Other creatures in our world clearly do not have lungs, so they cannot use this method to disperse oxygen throughout their bodies. In particular, the way insects breathe is interesting to study.

Insects breathe or collect oxygen through a branching network of tubes called tracheas. These tubes have openings, called spiracles, located in the chest (thorax) and abdomen. Oxygen passively enters the spiracles, flows through the tubes, and ends up in the liquid located at the bottom of each tube that helps dissolve the oxygen. This liquid then moves to other cells to supply oxygen to other cells in the insect’s body.

You can see, under a microscope, insects breathe or inhale air through their mouths, but they rarely yawn. And that mouth air doesn’t provide the oxygen needed by the cells because insects don’t have lungs. Instead of using air in the mouth to deliver oxygen to the lungs, insects can be said to breathe passively. They need to rely on the oxygen around them entering their spiracles, going down their windpipes to provide the oxygen needed for all of their cells.

What makes the subject of how insects breathe fascinating is that, theoretically, insects in a highly oxygen-rich environment could technically become much larger than today’s modern versions. For example, many paleontologists suggest that many of our modern insects are tiny versions of giant insects that may have roamed the Earth in prehistoric times. Due to the insects’ passive breathing mode, life cannot be sustained when the insects are too large, as there would be no way to adequately oxygenate all the cells. Scientists believe that Earth used to have a much higher oxygen content, however, meaning there was a proliferation of oxygen for insects to absorb. That alone could explain why the creepy crawlies of the past were so big – they had more air available to “breathe”.

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As oxygen levels declined on Earth, being of smaller size would have been an advantage for the insect. As insects couldn’t breathe as much, survival may have been based on being more compact to provide healthy oxygenation to all tissues. Although it must be stated that there are still some pretty big insects in the world. Most, however, are not as large as those found in the fossil record.

For example, the largest dragonfly fossil found is believed to have lived 250 million years ago, during the Paleozoic Era. Its wingspan was 30 inches (76.2 cm) and body length 18 inches (45.72 cm). Clearly, the oxygen-rich environment and the way insects breathe benefited the first dragonfly, which had a wingspan almost as big as a child’s height.

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