Life is a diverse and fascinating mystery populated by a rich tapestry of organisms—from unicellular bacteria to insects and even you and me.
As different as all these lifeforms are, though, we all share something in common.
We have to breathe! Mammals, like humans, breathe using lungs but what about bugs? How do they breathe?
Insects don’t breathe like humans or other mammals.
Instead of using lungs and a cardiovascular system to transport oxygen throughout their bodies, they rely on simple gas exchanges to take in oxygen and release carbon dioxide.
This is thanks to their unique anatomy and physiology.
Let’s take a look at seven amazing facts about bugs and how they breathe:
- Insects do not breathe using lungs
- Insects can control their respiration
- Some insects hold their breath for days
- Many insects can breathe in water
- Some insects have gills
- Some insects use a snorkel
- Some insects SCUBA dive
Insects Do Not Breathe Using Lungs
Compared to insects, mammalian respiratory systems are pretty straightforward. We push and pull air through our nostrils and mouth by contracting and relaxing our diaphragms.
As air enters our capillary-rich lungs, blood cells exchange carbon dioxide waste with fresh oxygen.
Our blood is then pumped through our hearts and back around the body before returning to our lungs for more oxygen.
Insect respiratory systems, on the other hand, are completely separate from their circulatory systems.
Instead of relying on the heart and lungs, insects use an intricate system of tracheal tubes that carry oxygen throughout their bodies.
Oxygen enters their bodies as they move and carbon dioxide exits at the same time.
Furthermore, insects do not breathe through their mouths.
Instead, their outer exoskeletons are dotted with several lateral openings called spiracles that allow air to enter their bodies.
Each body section—thorax and abdomen—typically has a single pair of spiracles.
As air enters a spiracle, it passes through a tracheal trunk that extends vertically across the insect’s body.
As the air moves through the tube, oxygen diffuses throughout an intricate network of branching trachea that breaks off into ever-smaller sections.
At the end of each branch, a tracheole allows for different gasses to be passed across a thin, moist membrane.
Oxygen diffuses across the tracheole’s liquid membrane where it then mixes with the cytoplasm inside an insect’s cells.
As oxygen crosses into the animal’s cells, carbon dioxide crosses over the membrane where it will then move out through the same branching tracheal system.
Insects Can Control Their Respiration
At first glance, it may seem as though insects breathe passively—as if the air just washes over their bodies and they naturally absorb oxygen from it.
While some small insects can survive by just moving through the air and allowing oxygen to passively enter their spiracles, larger insects can control their breathing, just like you and me.
This is called active ventilation!
When insects face the stress of prolonged activity or extreme temperatures, they can actively control their respiratory systems by opening and closing their spiracles.
Using their abdominal muscles, they can selectively close or open a spiracle and begin pumping their abdomens to either contract or expand their bodies.
As their bodies pulsate, air flushes throughout their intricate tracheal systems at a faster rate.
However, insects are still limited by the amount of oxygen and carbon dioxide that can diffuse across their tracheole membranes at any given time.
For this reason, insects can’t grow much bigger than they already are.
If they were any bigger, it would take far too long for oxygen to reach their systems.
Some Insects Can Hold Their Breath for Days
As unbelievable as it may sound, scientists have known for decades that many insects can go without respiration for hours and even days.
To put that in perspective, the longest record of a human holding their breath was 24 minutes and 37 seconds.
That’s 58x shorter than what average insects are capable of.
Insects can get away with this thanks to the superior efficiency of their respiratory systems.
As long as they remain at rest, they can stop taking in oxygen and passively release carbon dioxide across their tracheole membranes.
In fact, some insects have to close off of their spiracles because too much oxygen can be deadly.
The efficiency of an insect’s respiratory system allows them to pull in a higher volume of oxygen per respiration, proportional to their size.
That oxygen then goes directly to their organs and systems rather than dissolving into the blood.
But remember, insects are much smaller than humans.
If you were to consume a massive amount of oxygen, your tissues would begin to undergo oxidative damage and die.
The same goes for insects but on a much smaller scale. They need far less oxygen and, therefore, can go without it for longer.
Many Insects Can Survive Underwater
You have surely seen beetles swimming in water or dragonflies skimming across the surface of a pond.
But did you know that many insects can survive underwear for extended periods?
After learning that insects can hold their breath for days on end, it should come as a surprise that they can also dive deep without worrying about oxygen.
Although it may seem like some insects are actually breathing underwater—especially insects that go through aquatic larval stages—they can’t breathe underwater like a fish or an amphibian.
Instead, they make use of their highly efficient respiratory systems to close off their spiracles and undergo discontinuous gas exchange.
While underwater, an insect can continually recycle a large volume of oxygen in its branching tracheal network.
This is also true of insects that bury deep into the ground where there’s very limited oxygen.
When they are ready to take a fresh breath of air, they can resurface and begin a new cycle of respiration.
Some Insects Have Gills
This is where things get weird.
Although most insects can survive underwear for extended periods by simply relying on their highly efficient respiratory systems, some species of insects have evolved to have a set of gills. These include:
- Water bugs
Just like fish, these insects use a complex set of biological gills to breathe underwater.
A biological gill is a specialized organ developed to dissolve oxygen across the insect’s exterior membrane into its body.
Whereas fish have gills on their sides, insect gills are usually an extension of their tracheal system.
For damselflies and mayflies, this looks like a small leaf shape located towards their rear end or on the sides of their abdomens.
By continuously waving their gills, they can create a constant flow of oxygenated water across their bodies.
Not all insects have the same style of gills though. With caddisflies and stoneflies, their gills are located on their thoraxes and abdomens.
Dragonflies are unique because their gills are internal and located in their rectums.
By contracting their abdomens, they can circulate water through their anuses, thus diffusing oxygen into their bodies.
But what’s most amazing is that dragonflies can use their anal circulating system as a jet pack, quickly propelling them away from danger.
Other Insects Prefer to Use a Snorkel
As fascinating as it is to consider that some insects have developed gills like a fish, the overwhelming majority of aquatic insects live underwater by using the animal kingdom’s equivalent of a snorkel—a siphon.
Essentially, their bodies have evolved to have a thin, hollow tube through which they can breathe fresh air.
Consider mosquito larvae. They are arguably one of the most well-known insects to live and grow in the water.
Yet, they don’t have gills like a dragonfly or damselfly.
Instead, their rear ends have a hollow siphon tube that pulls in air and allows them to grow into adult mosquitoes. They’re not the only ones though:
- Water scorpions
- Rat-tailed maggots
- Tabanid flies
To keep water from splashing into their breathing tubes, insect siphons have a tightly packed ring of hairs that are coated with waterproof compounds.
The insect can simply jut their siphon through the surface of the water and passively absorb air through the tube.
If the insect wants to dive deeper into the water, simple pressure pushes the ring of hairs together, sealing off their siphons and keeping the water out.
In fact, sealing oxygen into their siphons allows some insects to maintain buoyancy while also maintaining a supply of oxygen so they don’t have to resurface for air.
Some Insects Prefer to SCUBA Dive
If snorkeling insects sounded absurd enough, wait until you hear about deep-diving SCUBA bugs.
Of course, we don’t mean that they’re carrying tanks and breathers below water.
Instead, SCUBA—self-contained underwater breathing apparatus—simply refers to a way for insects to carry a fresh supply of oxygen with them as they dive below the surface.
Some water bugs can carry a small air bubble below the surface, from which they can breathe while underwater. These include:
- Diving beetles
- Water boatmen
They trap the air bubble below their wings or carry it against their exoskeletons using specialized hairs.
By affixing it against one of their spiracles, they can continue to breathe, even while in the water.
Although a single air bubble won’t provide much oxygen, water’s unique properties allow more oxygen molecules to dissolve back into the bubble, thus refreshing their oxygen supply.
If the insect can create a larger bubble, it’ll be able to stay underwater for even longer.
More surface area means that more oxygen will dissolve across the bubble’s membrane and back into the air within it.
However, it’s not a permanent solution. Eventually, the bubble will shrink as nitrogen dissolves out from the bubble and into the water.
As the bubble shrinks, the insect must resurface for air.
Nonetheless, some diving beetles have been recorded staying below the surface for up to 36 hours!
While it’s not a long-term solution, their SCUBA gear will certainly keep them going for as long as they need.
Final Thoughts on Insect Respiration
Although insects seem like simple animals, they’re far more intricate than we give them credit for.
Despite lacking a united cardiovascular and respiratory system, insects somehow manage to outdo mammals with their ability to breathe and exist without oxygen for long periods.
Thanks to their highly efficient system of branching trachea, insects can go days without air, survive underwater, and have even developed complex systems such as biological snorkels and the ability to create air bubbles around their siphons.
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