How Many Legs Do Millipedes Have?

Millipedes don't literally have a thousand legs, but how many do they really have? Learn about these fascinating arthropods in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of iHeartRadio. Hey brain Stuff,
Lauren bog obamb Here. Let's start with the basics. Millipedes
are not worms, nor are they insects. Insects have six legs,
and obviously millipedes have many more. But exactly how many
more The answer may vary by the particular specimen in question,

(00:22):
but it's never going to be nine ninety four. It
turns out that no one chose their name millie meaning
a thousand, and pedes referring to feat as a way
to convey the precise number of legs. These organisms have
their cousin, the centipede, with the prefix centi meaning a hundred,
are similarly named by way of illustration, not precision. Millipedes
fall within a subphylum of arthropods. All arthropods have in

(00:45):
common a hard exoskeleton, segmented bodies, and jointed legs, like arachnids, insects,
and crustaceans. What distinguishes millipedes is that they have many
segments in their body, and for each segment, they have
two pairs of legs instead of one pair, as you
would see with say, centipedes having so many legs as
part of what makes millipedes so adaptive. Fossil evidence suggests

(01:05):
that millipedes were among the first ever terrestrial animals, which
means they've been around for about four hundred million years.
Back in the Coniferous Period, about three hundred million years ago,
a millipede species known as arthur Plora grew to an
enormous six and a half feet long and one and
a half feet wide that's about two meters by a
half a meter. Today, millipedes range in size, thank goodness,

(01:25):
from just a tenth of an inch or three millimeters
to about eleven inches or a third of a meter.
So far, researchers have discovered about twelve thousand species on
every continent except Antarctica, but estimate that there could be
as many as eighty thousand species here in the United States,
every state has some species of millipedes that are unique
and can't be found anywhere else. Scientists have developed new

(01:46):
imaging techniques that use u VY light to help them
differentiate between millipede species. This approach works because millipede exoskeletons
and reproductive organs glow under u VY light, as is
the case with many other arthropods like scorpions. Some species
of millipede in California, however, are bioluminescent, which means they
glow in the dark. Millipedes feast on leaf litter that's
plentiful around the world. This means millipedes spend most of

(02:09):
their time in soil, under leaves and rocks. And what
makes them so effective at getting around in this dense
habitat is there many mighty legs. They use the first
segment of their body like a bulldozer, and having so
many legs means they have a lot of power with
which to push burrowing through the dirt. When millipedes hatch,
they have only a few pairs of legs. Then, just
like many other arthropods like crabs and spiders, they grow

(02:32):
through a process called molting. This process involves shedding their
exoskeleton and growing a new one. Each time they do this,
millipedes also grow a new segment and therefore two new
pairs of legs. Some millipedes stop molting when they reach adulthood,
and others molt their whole lives, which is on average
about two years. So how many legs to millipedes have

(02:52):
it depends on the group, but it ranges between twenty
four and seven hundred and fifty at most, though that's uncommon.
Most millipede species have under a hundred legs. Millipedes have
some defense mechanisms, but they don't bite or sting. They
have very poor eyesight. Some species have no eyes at
all and mostly just use their antenna to find their way.
A millipedes best move when it feels threatened is to

(03:13):
curl up in a ball and secrete chemicals that ward
off predators. The chemicals they secrete vary, but are released
in such tiny quantities that they're generally not hazardous to humans.
Some research describes how in certain tropical regions, monkeys actually
seek out millipedes and use the chemicals they secrete as
mosquito repellent. Centipedes, by contrast, can bite using small things
that do secrete venom. Even then, while a centipede bite

(03:35):
can be painful, it usually won't cause other harmful effects.
If you're looking to tell the difference between a centipede
and a millipede, legwise, centipedes legs tend to spread out
to their sides, while millipedes legs point downward. Centipedes only
have one pair of legs per segment, while millipedes have
two pairs. If you're not keen on getting close enough
to check, observe the creature's behavior. If it runs away quickly,

(03:56):
it's likely a centipede. If it just curls up, it's
probably a millipede. Today's episode was written by Danielle Duez
and produced by Tyler Clang. Brain Stuff is a production
of i Heeart Radio's How Stuff Works. For more on
this in a multitude of other topics, visit our home
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(04:18):
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