This (above) is a flat-backed millipede. Problem is that rather than looking like a ‘normal’ millipede, it does look an awful lot like a centipede. Flattened body, undulating movement. Both centipedes and millipedes are arthropods (they are invertebrates but they are not insects) – and many people probably assume that ‘centi’ (meaning hundred) and ‘milli’ (meaning thousand) relate to the number of legs of each creature but the numbers of legs actualy vary greatly from species to species, and while there are centipedes with more than 100 legs, there are no millipedes with as many as a thousand.
So what’s the REAL difference? The clue is in their scientific names – Centipedes are Chilopods (meaning lip-foot) and millipedes are Diplopods (meaning double-foot), and this ‘double-foot’ name comes from the number of pairs of legs on each body segment. It sounds a bit complicated, but is easily visible to the naked eye, and obvious with a hand lens. Take a look:
Centipedes and millipedes’ bodies are divided into many segments. You can see these in colour in the photos above. Centipedes (on the left) have one pair of legs on each segment – one leg on each side of the body, while millipedes (on the right) have two pairs of legs on each segment (ergo ‘double foot’!). You can see it best when you view the creatures from below:
There are several other differences: Centipedes tend to have long antennae while millipedes have short ones. Centipedes are predators while millipedes are scavengers. But by far the most important difference is that you can safely pick up millipedes, but a centipede is quite able (and usually willing!) to give you a nasty bite!