Myriapods are arthropods known for their impressive number of jointed legs. Their name comes from Greek and means “10,000 feet,” although no documented species has anywhere near that many.
All myriapods are land-dwelling. They are typically found in soil, leaf litter, under stones, or beneath rotting wood. Many species have glands that release repellent substances when they feel threatened.
This large group is divided into four classes: millipedes (Diplopoda), centipedes (Chilopoda), pauropods (Pauropoda), and symphylans (Symphyla).
Millipedes
Better known as millipedes, diplopods are the largest group of myriapods, with more than 13,000 known species. They are most diverse in warmer regions.
Despite the common name “millipede,” only one species has more than 1,000 legs, with just over 1,300.
In these arthropods, most body segments in adults carry two pairs of legs. That’s why they are called diplopods, a name that means “double foot.”
Some millipedes feed on fungi or other arthropods, but most eat decaying organic matter. Millipedes are also harmless to humans.
Centipedes
With more than 3,100 species, centipedes are the second-largest group of myriapods. Unlike millipedes, they have one pair of legs per body segment.
Their legs are long and strong, allowing them to move faster than millipedes. Surprisingly, the fastest species are often the ones with the fewest legs.
The largest centipedes can reach 30 cm in length and have at most about 350 legs.
Centipedes are almost all predators. Their first pair of appendages is modified into hook-like claws called forcipules, which contain venom glands. These claws can help with defence, but they are mainly used to capture and paralyze prey, most often other arthropods.
On rare occasions, some centipedes may feed on plant material.
Pauropods
With more than 900 species, these tiny decomposers are less than 2 mm long. Their bodies are short and sometimes flattened.
As adults, pauropods have 18 legs, or more rarely 20. The larvae, which have 12 legs, are often mistaken for six-legged insects or for 14-legged woodlice.
Because they are so small and avoid light, pauropods are difficult to observe. As a result, even though several species are found in Quebec, these arthropods remain little known.
Symphylans
With more than 200 species, symphylans look like a pale, eyeless, more primitive-looking version of centipedes.
They usually have 24 legs, sometimes 22, and grow to about 2 to 8 mm long.