The millipede – sometimes referred to as “the hundred-legged creature” – is neither a worm nor an insect. Insects only have six legs, and it’s clear that millipedes have far more than that. So, exactly how many legs do millipedes have?
Many people respond with 994 due to the Latin prefix “milli-“ (meaning 1,000) in the creature’s name, but they are mistaken.
It turns out that scientists did not choose the prefix “milli-“ to represent the actual number of legs this organism has. The common name for the millipede, “the hundred-legged creature”, is also inaccurate.
The specific identifying feature of the millipede is that each body segment has two pairs of legs.
Millipedes are part of the arthropod group, which is a diverse group of invertebrates that includes spiders, scorpions, and butterflies. All arthropods share common characteristics such as an exoskeleton, a segmented body, and jointed legs. In contrast, the specific identifying feature of the millipede is that each body segment has two pairs of legs, unlike the single pair found in centipedes. This explains the more accurate scientific name used by researchers: Diplopoda, meaning “double legs.”
The large number of legs is a factor that helps millipedes adapt to their environment. Fossil evidence shows that millipedes were among the first terrestrial animals, meaning they have existed for about 400 million years.
During the Carboniferous period, around 300 million years ago, a species of millipede known as Arthropleura grew to a length of 2 meters and a width of 0.5 meters. Today, millipedes only range in size from 3mm to about 0.3 meters. To date, scientists have discovered approximately 12,000 species of millipedes across all continents except Antarctica, but it is estimated that there could be as many as 80,000 species of these creatures.
“Each country has only a few species of millipedes that are found there and not anywhere else,” says Derek Hennen, a PhD candidate in entomology at Virginia Tech. Hennen studies millipedes and loves them so much that he created a Twitter account (@DearMillipede) dedicated to all things related to these animals.
Why Do Millipedes Have So Many Legs?
Millipedes feed on decaying leaves, which are scattered everywhere despite being low in nutrients. This means that millipedes spend most of their time underground, beneath leaves and rocks. What allows them to move easily in this harsh living environment? Of course, it’s thanks to their pairs of legs.
Hennen states: “The collum (the first body segment) acts like a bulldozer, and having many legs helps the millipede push its body and burrow deeper into the ground.”
The number of legs a millipede has depends on the species.
When millipedes hatch, they only have a few pairs of legs. Later, like many other creatures such as crabs and spiders, millipedes mature through a process called molting. During this process, millipedes shed their exoskeleton and develop a new one. Each time they do this, they also grow a new body segment along with two new pairs of legs. Some millipede species stop molting once they reach adulthood, while others continue to molt throughout their lives, averaging about two years.
<pSo, how many legs do millipedes have? Hennen reveals that this depends on the species, but the number of legs ranges from 24 to 750.
Hennen adds: “I guess those who have seen this might have exclaimed, ‘This one really has a lot of legs!’ which is how the common nickname came to be. While it might sound complicated, millipedes are essentially similar to centipedes, just with more legs.”
In reality, most millipede species have fewer than 100 legs.
The Difference Between Millipedes and Centipedes
Millipedes have several defensive mechanisms, but they do not bite or sting (they have very poor vision, with some species lacking eyes altogether and primarily using antennae to navigate). The optimal defense reaction for millipedes is to curl up and secrete chemicals that repel predators when they feel threatened. While the chemicals millipedes secrete vary, only a small amount is released, which usually does not pose a danger to humans. Many studies describe how in certain tropical areas, monkeys seek out millipedes to utilize the chemicals they secrete to repel mosquitoes.
In contrast, centipedes can bite with their small fangs that secrete venom. However, even if a centipede’s bite is painful, it is not harmful to us.
In terms of legs, centipede legs tend to spread out, while millipede legs hang downwards. Centipedes have one pair of legs per body segment, while millipedes have two pairs. If you don’t want to get too close just to verify this, Hennen suggests observing the behavior of the creatures. If the creature runs quickly, it’s a centipede. If it curls up, it’s a millipede.
