Can Millipedes Swim? For How Long? How Do They Breathe?

A millipede walking along the edge of a shallow stream.

Millipedes have nearly countless legs and are in a constant search for moisture.

They have powerful bodies and are capable of burrowing, climbing, and facilitating the decomposition of soil.

Does this mean that they are strong swimmers, capable of taking over your backyard pool? 

Can millipedes swim? Millipedes can only swim for a short period of time. They breathe oxygen through spiracles located at the base of their legs, so if they remain submerged in the water for more than a few minutes, they are unable to access oxygen, and they will drown. 

For being such small creatures, millipedes really are quite complex and have special requirements in order to survive.

It’s almost ironic that millipedes actively seek out moist conditions but are unable to remain in the water for long.

In the following, we’ll explore this more and learn some other fascinating facts about these strange, but interesting, little arthropods.

Can Millipedes Breathe Underwater?

Millipedes are not good swimmers. They are terrestrial creatures, which means they are built to live on land.

They breathe through spiracles, not with nostrils and lungs like humans.

Spiracles are minuscule external respiratory openings controlled by one or two muscles.

Millipedes have two pairs of spiracles and legs on each body segment, with the spiracles situated just above and often slightly in front of the base of the legs.

(Don’t confuse millipedes with the centipede, which has fewer legs. Learn their similarities and differences here.)

Millipedes use these openings to draw air into internal pouches.

The air is then distributed to the trachea, which transports the gas (oxygen) to all of the cells, tissues and organs in the body.

Because millipedes use oxygen to breathe, they cannot survive for long underwater.

Like humans, their system cannot process water, and they will eventually drown.

Though millipedes might have up to 750 legs, they are not built for swimming.

The legs are short, thin, and do not move in a swimming motion.

Millipedes are not strong swimmers and cannot move quickly in water. 

Some millipedes found in floodplains can apparently survive in extremely wet environments for several months. 

These species are hardy and have adapted to extreme habitats, but even they cannot breathe underwater.

Why Do Millipedes Get Into Swimming Pools?

If you have a pool, you might occasionally see millipedes attempting to swim or drowned at the bottom. There are a couple of reasons for that.

Remember that millipedes are constantly seeking moisture, which of course can be found in a pool.

Even though this body of water will kill them, they cannot tell the difference and will fall in before they have realized what happened. 

To prevent millipedes from seeking the moisture in the pool, keep surrounding grass, flowerbeds, and gardens watered consistently.

Since millipedes, like earthworms, are helpful to the soil, you want these bugs to remain in the ground where they belong and away from the pool.

Also, keep in mind that millipedes are attracted to decaying plant matter.

If your pool is located underneath trees, be sure to remove fallen leaves and sticks from the pool.

Remove grass and other organic material from the pool in a timely manner.

Algae can also be a part of the millipede diet, so make sure that the pool chemicals are up to date, utilizing a professional expert to help ensure the water is safe and clean.

Clean your pool filter routinely, as it can often build up with grass, leaves, and other such material, attracting millipedes.

When millipedes drown, they might float on the surface of the pool, or they might sink to the bottom. Use a good pool vacuum or net to remove the bodies. 

If you have an in-ground pool, consider keeping organic material away from it to make the area less appealing to millipedes.

Use pea gravel, attractive rocks, or other non-organic materials in flower beds near the pool.

Keep any potted plants that are near the pool watered enough for millipedes to remain in the soil.

Where Do Millipedes Live?

Though millipedes cannot survive in bodies of water, they need moist and humid environments to survive.

This is because they are unable to retain moisture for long periods of time, so they are in constant need of water in their location.

Millipedes can be found on every continent except Antarctica, with an estimated 80,000 species in existence. 

Millipedes need the moisture found in healthy soil. They burrow underground and lay their eggs in places replete with food sources.

They are not aggressive and their best defenses are curling up in spirals to hide behind their hard exoskeleton and secreting a cyanide-like liquid to discourage predators.

Because millipedes make the decomposition process happen more quickly than it naturally would, they are extremely beneficial to the ecosystem.

When their habitat becomes too dry to be sustainable, they might seek the dampness found in many basements or crawlspaces.

On the other hand, if there have been excessive amounts of rain, they may seek entrance to your home because the ground is too wet and thus, is uninhabitable.

Extreme saturation of the ground could also cause millipedes to seek higher ground such as concrete slabs, siding, or drainpipes.

How Long Do Millipedes Live?

With an appropriate habitat and diet, millipedes can be expected to live for one to ten years.

Most species are not very hardy, however, and cannot survive much adversity.

They will die in a couple of days (if not in a couple of hours) if they cannot obtain the necessary moisture and nourishment.

What Do They Eat?

Millipedes are classified as detritivores, which means they eat primarily decomposing organic material such as:

  • Dead grass.
  • Leaf litter.
  • Old root systems.
  • Mulch.
  • Rotten wood.
  • Stumps.
  • Compost and wood piles.
  • Garbage.

They also shed their skin as they grow, and several species will consume the old skin to obtain calcium.

They do not typically eat growing, living plants (although in times of extreme drought they might eat young plants to obtain moisture), so they are not considered harmful to crops or gardens.

Some species, however, have been known to wreak havoc on greenhouses and other environments with young seedlings, eating them for moisture and nourishment.

How Can I Keep Millipedes Out of My House?

Because millipedes need moisture and decomposing plant material to survive, the best way to ensure that they do not come inside is to keep the things that attract them away from your home.

This includes moving all forms of decaying plant material away from the foundation of the house.

Don’t overlook food sources such as dead grass, leaf litter, old root systems, mulch, rotten wood, stumps, compost piles, chopped wood, and garbage. 

You’ll find a comprehensive guide to getting rid of millipedes here with additional prevention tips and recommended products for eliminating them, including natural options.

Since millipedes search for moisture, make sure your basement or crawlspace is as dry as possible.

Consider using a dehumidifier inside and using drainpipe extensions to direct rainwater and snowmelt away from the house’s foundation. 

Millipedes are skinny and crafty, making it difficult to determine exactly where and how they enter the house.

However, if there are any obvious cracks or seams on the exterior of your house, make sure they are sealed completely.

Use effective weather stripping at the bottom of exterior doors.

If these methods fail, there are also pesticide options. Read this article to see which products we recommend for millipede elimination.

Look for trusted brands, such as Ortho Home Defense, and follow all instructions and warnings carefully.

Always keep harmful chemicals away from children and stored in a safe location.

Conclusion

Millipedes are built for burrowing in the soil, eating, and processing decomposing plant matter to speed up the ecological process.

They are poor swimmers who, similarly to humans, cannot survive more than a couple of minutes underwater.

Their need for moisture might cause them to crawl or fall into a swimming pool or other body of water, but they will ultimately drown quickly. 

You likely have other questions about millipedes.

Be sure to check with all of our millipede articles to find the answers you’re looking for. Click here to view them all.

Related Questions:

Can Centipedes Swim?

Centipedes are similar to millipedes in several visible ways, but they are different animals belonging to a separate scientific classification.

Just like millipedes, however, centipedes swim poorly due to their body structure, are unable to breathe in the water, and cannot survive underwater for longer than a couple of minutes. 

Can Millipedes Regenerate Body Parts?

Millipedes are capable of regrowing lost body parts as they use molting to grow.

They typically molt in underground nest areas, since they are susceptible to attacks while shedding their exoskeleton.

When millipedes hatch from eggs, they only have six body segments and three pairs of legs.

They grow more segments and more legs each time they molt until they reach the adult stage of life.

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