Someone posted the question online: does a house centipede have more legs than a centipede? The answer is weirder than you'd expect — because "centipede" turns out to be a whole family of animals with wildly different leg counts, from 15 pairs all the way up to 191.
The House Centipede: 15 Pairs, Grown Over Time
Meet the house centipede first. An adult has 15 leg-bearing segments, each carrying one pair of legs — the pair on the very end breaks off easily (the one in this photo already lost it). Its back plates are unusual: only eight plates, which do not match the segments underneath. So even with every leg gone, you could still recognize it.
House centipedes also grow new segments as they age — but only until adulthood. A freshly hatched one has just four pairs of legs, an accidental spider costume. Juveniles are rarely seen.
The Centipede: 21 or 23 Pairs, Fixed at Birth
Most centipedes have 21 pairs of legs; some have 23. That number is fixed from birth. The juvenile in this photo is a rough-eared centipede (Otostigmus scaber); the other common type, the sharp-jawed centipede, carries 23 pairs.
Those "Legs" Near the Head
Both house centipedes and centipedes have one extra pair of special legs at the front — venomous, claw-like, used for hunting. Strictly speaking they are not counted as real legs, and this is how the animals inject venom: not through fangs, but through these legs.
The Question Doesn't End There
The family gets stranger.
Stone centipedes also have 15 leg-bearing segments and 15 pairs of legs, but their back plates alternate large and small — except where two large ones sit together, which looks bizarre up close. After house centipedes, they are the most primitive group.
Cup centipedes are living fossils: only two species survive, found in Tasmania and New Zealand. They hatch with 12 pairs of legs and grow to 15 after a single molt — halfway between primitive and modern patterns.
Soil centipedes are the newest branch, and they somehow unlocked the segment limit. They can carry anywhere from 27 to 191 pairs of legs — always an odd number, for reasons nobody knows. The count is fixed at birth and never changes after molting. Burrowing in soil has deformed them oddly: long, thin, flattened, with very short legs — and a head shaped like an extended shovel.
