Millipede: What It Is, Why It Comes Indoors, and How to Keep It Out

What is a millipede?

A millipede is a soil animal with a long, segmented body and two pairs of legs on most of its body rings. Scientists call the group Diplopoda, which means “double legs”. The ones you find at home are usually 1/2 to 1 1/2 inches (13 to 38 mm) long, brown to black, and slow.

Millipedes live in damp leaf litter, mulch and rotting wood, where they eat dead plant material. In other words, they are recyclers. People also call them “thousand-leggers” and “wire worms”.

You can tell a millipede by four things. First, it moves slowly, with its legs rippling in a wave under the body. Second, the legs are short and sit underneath, not out to the sides. Third, it has short antennae. Finally, it coils into a flat spiral when you touch it, and dead ones are usually found curled the same way. Counting legs is the first step in our six checks for naming any bug, too.

Sizes vary a lot between species, from 2 to 280 mm (0.08 to 11 inches) worldwide. However, the ones that wander into houses are small: the garden millipede is 1/2 to 3/4 inch, and the brown species most often found in homes is about 1 to 1 1/2 inches.

How many kinds of millipedes are there?

Sources disagree, because new species are still being described. The National Wildlife Federation says 7,000, Britannica says about 10,000, and the Wikipedia summary of the research says about 12,000 named species. Estimates of the real total run as high as 80,000.

North America has plenty of its own: about 230 species live in the southern Appalachians alone.

How many legs does a millipede have?

Common millipedes have between 34 and 400 legs, not 1,000. The record belongs to Eumillipes persephone, found in 2020 in Western Australia, with 1,306 legs. Until then the record was 750, held by Illacme plenipes from California. A common yard millipede has about 160.

The name means “thousand feet”, but almost no millipede comes close. In 2021 a team led by Paul Marek described the record holder in the journal Scientific Reports. It lives 60 m (about 200 feet) underground in a mining drill hole, is blind and pale, and one female had 330 body rings and 1,306 legs.

For the millipedes in your yard, the number is much smaller. Across all species the range runs from 22 to 750 legs, and common species sit at 34 to 400.

How the legs are arranged

Each ring carries two pairs of legs, except at the front. The first ring behind the head has no legs, and the next three rings have one pair each. That front section is why people sometimes say millipedes have “one or two” pairs per segment.

The double rings formed long ago, when pairs of segments fused. So most rings after the fourth have four legs, two on each side, and the last ring has none. By contrast, a centipede has one pair per segment. That one feature separates the two faster than anything else.

Why does a millipede keep getting more legs?

A millipede adds legs as it grows, hatching with only three pairs. Then, each time it molts, it adds new rings and new legs. Scientists call this anamorphosis. So two millipedes of the same species can have different leg counts, depending on their age.

Many sources get the leg count wrong

Even good references disagree here. UC IPM says even the largest millipedes have “somewhat fewer than a hundred” legs. Britannica says “as many as 200 pairs”. However, both figures fall short of the 750-leg Illacme plenipes, which has been known for years, and the 1,306-leg record from 2021.

Are millipedes insects?

No. Millipedes are not insects. Insects have 6 legs and three body parts, while millipedes have dozens to hundreds of legs and a long body of many rings. Millipedes belong to the class Diplopoda, inside a group called myriapods, which also holds centipedes. Both are arthropods, like insects, spiders and crabs.

Unlike insects, millipedes have numerous body segments and numerous legs, and no wings at any stage. Our insect identifier shows how to sort insects from the other many-legged groups.

You may read that millipedes are closer relatives of lobsters and shrimp than of insects. The National Wildlife Federation says so, for example. But a large DNA study by Regier and others, published in Nature in 2010, found the reverse. Insects and crustaceans form one branch together, and the myriapods sit on a separate branch beside it. So a lobster is closer to a beetle than to a millipede.

Millipede or something else?

A millipede has two pairs of short legs on most body rings and moves slowly. By contrast, a centipede has one pair of long legs per segment and runs fast. A wireworm has only 6 legs, and a pill bug has 7 pairs. If it coils into a flat spiral, it is almost certainly a millipede.

People who find millipedes indoors often call them worms or caterpillars. In fact, one Ohio homeowner wrote to Ask Extension that the house was “overrun by the caterpillar(?)”. The expert’s answer was short: “This is not a caterpillar but a millipede.”

Millipede vs centipede

The quickest test is the legs. A millipede has two pairs per body ring, tucked underneath, and walks slowly. A centipede has one pair per segment that sticks out to the sides, and it runs. Also, a centipede has a pair of venom claws behind its head and can bite, while a millipede cannot.

Diet differs too. Millipedes eat dead leaves and rotting wood, so they are recyclers. Centipedes hunt other bugs, so they are predators. A third check: centipedes have long antennae, and millipedes have short ones. Our centipede guide covers the fast one in full, including whether its bite matters.

Millipede or wireworm?

Wireworms are the larvae of click beetles, and people mix them up with millipedes because of their shape. But a wireworm has only 6 legs, all near the head. It is also usually dark yellow, and it stays below the soil surface rather than crawling across a floor.

Millipede or pill bug?

Pill bugs, or roly-polies, also roll up. However, they are crustaceans with 7 pairs of legs, and they curl into a ball rather than a flat spiral. A pill millipede can roll into a ball too, but the ones in North America are tiny and rarely seen. So a gray ball in your garden is almost always a pill bug.

The tiny bristly one: duff millipede or carpet beetle larva?

Duff millipedes reach only about 1/8 inch (3 mm) and are covered in bristles. They look like tiny carpet beetle larvae and sometimes gather near sinks and bathrooms. Both are harmless to people, but carpet beetle larvae eat wool, so it is worth telling them apart.

Types of millipedes you may see in the US

Most millipedes in and around US homes are one of a few types. The garden millipede, a flat-backed reddish-brown species about 3/4 inch (16 to 21 mm) long, is the most common one indoors. Outdoors you may meet larger ones, up to 4 inches (10 cm), and some brightly colored species that smell of almonds.

The garden millipede, the one in your house

The garden millipede is the species that most often invades homes in large numbers. It is also called the greenhouse millipede or flat-backed millipede, and it is native to Asia: 16 to 21 mm (0.6 to 0.8 inch) long, slightly flattened, and reddish brown to dark brown on the back.

It also gives off hydrogen cyanide gas when alarmed, says NC State. That is the faint almond smell some people notice when they sweep up a lot of them. Even so, the species is harmless, and it does not bite or sting.

Red millipedes

A large black millipede with red edges on its rings, in the eastern US, is most likely the American giant millipede. It is a 4-inch (100 mm) black-and-red species. A flat black millipede with red or orange spots is likely a cherry millipede. Both are outdoor species, and both are safe to look at but best not handled.

A small reddish-brown millipede indoors is usually the garden millipede. Its color ranges from reddish brown to dark brown, so it can look red under a kitchen light.

Millipedes that smell like almonds or cherries

Cherry millipedes and the yellow-spotted millipede defend themselves with hydrogen cyanide. Describing a related cyanide millipede, the Virginia Museum of Natural History says the smell is “a bit like almonds or cherries”. NC State says a similar flat black-and-yellow species, Apheloria tigana, is not hazardous to human health. Still, wash your hands after handling one.

Small and tiny millipedes

Most small millipedes you see indoors are young garden millipedes or the slim brown julids. Young millipedes are short because they add rings as they grow. The truly tiny, fuzzy one, about 1/8 inch or less, is the duff millipede. If you are unsure, our guide to small black bugs covers the other little dark things found on basement floors.

Are millipedes dangerous?

No. Millipedes do not bite or sting, and they carry no disease that affects people. The only risk is their defensive fluid, which can stain skin brown for weeks and can burn the eyes. So wash your hands after touching one, and rinse an eye with plenty of water for at least 20 minutes if fluid gets in.

Do millipedes bite?

Millipedes cannot bite people. They have no fangs and no stinger, according to a medical review in StatPearls. They do not bite when disturbed. Instead, a millipede coils up to protect its legs, and many species also ooze a smelly fluid from small pores along the sides.

What millipede fluid does to skin

The fluid can contain benzoquinones or hydrogen cyanide, among other chemicals, according to StatPearls. Benzoquinones stain the skin. MedlinePlus says the skin can turn brown, and StatPearls notes the stain can look like a bruise. On the toes it can even look like a circulation problem, as a 2014 case report on “blue toe” skin lesions describes.

The stain fades on its own. However, sources differ on how long it lasts: StatPearls says up to several weeks, while MedlinePlus says it may persist for months. Tropical species cause stronger reactions, with burning, blisters and itching, which doctors call millipede burn. Most species cause only a stain.

Are millipedes safe for kids?

Yes, with one rule. NC State Extension says children can safely handle millipedes, as long as they wash their hands afterward. Teach them not to rub their eyes after touching one. Also, a crushed millipede can leave a stain.

Can millipedes hurt dogs and cats?

US millipedes are rarely a problem for pets. NC State Extension says millipedes are not dangerous to humans or animals unless eaten in large numbers, and that pets usually avoid them because of the odor. Large tropical species are a different story: the University of Tennessee notes their spray has blinded dogs and chickens.

If your pet gets millipede fluid in an eye, or keeps drooling or vomiting after eating one, call your vet. You can also call the ASPCA Animal Poison Control Center at (888) 426-4435, where a consultation fee may apply.

Do millipedes damage your house or garden?

Indoors, millipedes do no damage. They are a nuisance and nothing more, and they do not infest food, fabric or wood. Outdoors, large numbers can damage sprouting seeds, seedlings, and strawberries that touch the ground.

Why are there millipedes in my house?

Millipedes come indoors by accident, usually when their outdoor home gets too wet or too dry. Heavy rain floods them out of the soil, and drought or cooler fall weather sets them moving. A moving millipede can cover 50 feet or more. They climb walls, slip under doors, and dry out and die indoors within a few days.

They live outdoors in damp places: leaf litter, mulch, compost, grass clippings, and under stones and boards. So a house with deep mulch or wet soil against the foundation has a big population right next to its walls. When that population moves, some of it ends up inside.

Why so many after rain?

Rain saturates the soil and leaf litter, and that drives the millipedes out. That is what extension entomologists reported after the heavy rains of June 2021, and an expert from Maryland Extension told one homeowner the same thing: in wet spring weather they come out in great numbers “as they try to escape drowning”.

Dry spells cause migrations too, so invasions follow both heavy rain and hot, dry weather. In the summer of 2015 it recorded masses of Pleuroloma flavipes in homes, schools and businesses in one county. Those that could not find moisture died of heat and dehydration.

Why in the fall?

Many people see the most millipedes in late summer and early fall. Migrations often follow cooler weather. They are looking for new places to feed and shelter, not for your house.

How do they get in?

Every way in is a gap: cracked foundations, openings under doors, open garage doors, windows, crawl spaces and window wells. They can climb about 6 feet up walls, fences and trees, so they may enter through high openings as easily as low ones.

Why are they in the basement or bathroom?

Millipedes need moisture, so the ones that get in head for the dampest spots. Basements, leaking appliances and damp boxes draw them. Those same damp corners also suit silverfish, so you may find both. That is also why the dead ones pile up in basement corners and along garage doors. One Maryland homeowner found thousands in the drain at the bottom of the outside basement stairs.

Can millipedes live and breed in your house?

No. Millipedes cannot survive long in the dry air of a house. They do not live more than a few days indoors, and they cannot reproduce inside. That is why you often find them dead and coiled, rather than alive.

What does it mean if you see a millipede in your house?

Millipedes in the house are a sign of damp, decaying material close to your foundation, not of a dirty home. In one Ask Extension case, a Maryland homeowner’s husband thought her composting was to blame. The expert said it was not the cause: “They are naturally there but are usually hidden.”

How many millipedes is too many?

Invasions are usually over within a few days. So patience is part of the plan, even when it feels like the house is under siege.

Where do millipedes live?

Millipedes live in all 50 US states, including Alaska and Hawaii, with about 1,400 species in the US and Canada. They need moisture, so they stay in damp places: under leaf litter, mulch, stones, logs and bark, and in compost and rotting wood.

They have no waxy coat to hold water in, so they dry out quickly. That is why they hide by day and come out at night or after rain. Garden millipedes also live on trees, in tree holes, and in clogged gutters.

Some live in odd places. The record-holding Eumillipes persephone lives in a drill hole 60 m (about 200 feet) underground. Others live in caves. And migrating millipedes sometimes fall into swimming pools and drown.

Are millipedes nocturnal?

Yes, most millipedes are active at night. That is why watering the lawn in the morning helps. That way, the grass has time to dry before they come out. During the day they hide under mulch, stones and leaf litter.

What do millipedes eat, and what do they do?

Millipedes eat dead plant material: fallen leaves, rotting wood, decaying grass and mulch. By breaking it down, they return nutrients to the soil, much like earthworms do. Each species can eat 1 to 11% of the leaf litter where it lives. Only in large numbers do they damage seedlings or strawberries.

Their role in the soil is bigger than most people think. Together, millipedes may eat nearly all the leaf litter in a region, which makes them an important part of nutrient cycling and soil health. The garden damage happens only when they become numerous.

That is the main reason not to spray them outdoors unless you have to. They are part of the cleanup crew in your flower beds.

What eats millipedes?

Birds, toads and small mammals eat millipedes. Reptiles, amphibians and some insects do too. One group of assassin bugs specializes in them. The coil, the hard shell and the bad-tasting fluid are all defenses against these predators.

Some animals even use that fluid: capuchin monkeys and lemurs have been seen rubbing millipedes on their fur, probably to keep mosquitoes away.

How long do millipedes live?

Most millipedes live 2 to 5 years, and some large species live over 10. Adults generally live 2 to 5 years, taking much of that time to mature. The American giant millipede has a recorded lifespan of 11 years. Indoors, though, a millipede survives only a few days.

The millipede life cycle

The female lays her eggs in the soil, often in small clusters. Females lay their eggs in small clusters of 20 to 100, and one female can lay as many as 300 at a time. The American giant millipede does it differently: it puts each egg in its own small nest of chewed leaves and droppings.

The young hatch after a few weeks with only three pairs of legs. Then they molt again and again, adding rings and legs each time. They eat their old skin after each molt to recover the nutrients. Depending on the species, they take from several months to about 5 years to become adults.

How to get rid of millipedes

To get rid of millipedes, sweep up the ones inside, then fix the outside. Clear a 12 to 18 inch (30 to 45 cm) dry zone along the foundation, keep mulch 2 to 4 inches (5 to 10 cm) deep or less, and seal gaps under doors. Indoor sprays are not needed, because millipedes die indoors within days.

All of these steps cost little or nothing. Every extension source puts moisture and shelter first, and pesticides last.

Should you use a pesticide?

Usually not. If exclusion and drying are successful, insecticide treatments are not required. Chemical controls are rarely warranted, and perimeter sprays have limited effect. Therefore, try the steps above first, and give them a few weeks.

If thousands still come in every year after that, the University of Tennessee says a pesticide can be applied around the outside of the house and near entry points. Rake back thick mulch first, so the product reaches the soil where millipedes live. It adds that a pesticide is only an add-on to sealing and drying, never a replacement. Use only an EPA-registered product labeled for millipedes, and follow the label exactly. The label is the law.

Natural ways to keep millipedes out

The most natural method is also the most effective: take away the damp shelter they live in. Deep mulch, wet leaves and plastic sheeting all keep the soil moist. In fact, Penn State Extension says gravel or mulch laid over plastic weed barrier creates good conditions for millipedes. So pulling up the plastic dries the soil out.

What does not work

Most of what fails against millipedes is aimed at the few you can see indoors. Those die within a few days anyway, so killing them changes nothing. The source is outside, in damp soil and mulch. Here are 8 common beliefs, several of them repeated on Reddit, and what extension experts say about each.

• Myth 1

  Myth: “Spraying inside the house will stop them.”

  Truth: Indoor sprays kill only the few you can see, and those would die within days anyway. Penn State Extension says indoor treatment is not necessary, and an Ohio Extension expert told one homeowner that sprays, fogs and bug bombs do not stop millipedes from getting into a home.

• Myth 2

  Myth: “They are breeding in my house.”

  Truth: Millipedes cannot reproduce in the dry air indoors, SDSU Extension says. Every one you find walked in from outside.

• Myth 3

  Myth: “Millipedes mean a dirty house.”

  Truth: They come from damp soil and leaf litter outdoors. A spotless house next to deep mulch will get more millipedes than a messy one surrounded by dry gravel.

• Myth 4

  Myth: “Plastic under the mulch keeps bugs away.”

  Truth: Penn State Extension says it does the opposite for millipedes, because the plastic holds moisture in the soil and blocks any treatment from reaching them.

• Myth 5

  Myth: “Millipedes have 1,000 legs.”

  Truth: Common species have 34 to 400. Only one known species, Eumillipes persephone, tops 1,000.

• Myth 6

  Myth: “A millipede can bite you.”

  Truth: It has no fangs and no stinger. The fluid can stain your skin, but that is the extent of it.

• Myth 7

  Myth: “Millipedes eat wallpaper and fabric.”

  Truth: The National Wildlife Federation says they do not infest food, fabric or wood. They eat dead plant material outdoors, and indoors they eat nothing before they dry out.

• Myth 8

  Myth: “Baking soda or a broadcast insecticide around the yard will fix it.”

  Truth: None of the extension sources we read recommend baking soda. A heavy spray across the whole yard also kills the millipedes that recycle your leaf litter, while the damp mulch that drew them stays. Dry the foundation zone and seal the house first.

When to call someone

Most millipede problems need a broom, not a professional. Call someone when thousands come in every year despite a dry zone and sealed doors, when fluid gets in an eye, or when a pet shows symptoms. For skin or eye exposure, Poison Control at 1-800-222-1222 is the first call.

Renters should tell the landlord about gaps and damp, because sealing and drying are what solve the problem. One Maryland homeowner had already paid for two exterminator visits. The Maryland Extension expert put it plainly: “You don’t need an exterminator, but someone to tighten up/seal the areas where they are entering.”

Not sure it is a millipede at all? Upload a photo to our free bug identifier for an answer in seconds.

Pest control disclaimer. Photo-based identification can help, but it is not always perfect. For dangerous spiders, large infestations, or anything you are unsure about, contact a licensed pest control professional.