MILLIPIDIES

Millipedes are relatively common litter and soil animals that occur in most parts of the world. The word 'milli' is latin for a thousand and 'pede' is for foot so a millipede ought to be a thousand footed animal. However whoever coined the name was guessing because although some millipedes have a lot of legs, none actually have a thousand.

In fact the record holder is Illacme plenipes which has an amazing 750 legs or 350 pairs. Most millipedes have far less than this though, normally 100 to 300. Millipedes are distinguished from all other Myriapods because they have two pairs of legs per body segment. This is because each segment is actually two segments fused together
.
These special segments are called 'Diplosegments' . Millipedes use their legs to push themselves into the soil, leaf litter or rotting wood, and the more legs you have the more you can push so it makes sense to have plenty of legs. Millipedes do not really need that many body segments though so the fusing of two segments into one functional unit whilst maintaining both pairs of legs allows millipedes to generate a lot of push without becoming impossibly long.

Though it is not visually obvious millipedes do have a what is called a thorax and an abdomen. The thoracic segments are the 1st 3 body segments, the rest are the abdominal segments. The 1st thoracic segment is apodous (without legs) and the 2nd and 3rd have only one pair of legs each. In all Millipedes except the Colobgnatha the anterior (front) pair of legs on the 4th body segment is also missing, hence if you want to know how many legs a millipede has you can count the number of body segments, multiply by 4 and subtract 10 unless it is a member of the colobgnatha in which case you only substract 8.