These amazing animals are AFRICAN GIANT BLACK MILLIPEDES, a species of which I have several adults named Millie, Molly, Martha, Maisie & Max.
At up to 35cm long these are true giants of the millipede world. When giant millipedes feel threatened, for example by their predators, they firstly coil their bodies into a spiral shape and protect their head inside the centre of the spiral as shown here:
If they continue to feel threatened they can produce very unpleasant smelling excrement along with a nasty smelling & tasting chemical from their bodies which causes any animal to be scared away, especially if they get it into their mouths!
Here is Millie doing her best impersonation of a ring doughnut!
As well as my group of adults I keep a number of other African giant black millipedes of various sizes, as I have been fortunate enough to have many groups of babies hatch in my collection during my time keeping them. Female African giant black millipedes lay their eggs just below the ground surface and these hatch into absolutely tiny white babies less than 3mm long; these are called protonymphs and have no eyes, no legs and are unable to move or feed! This stage of the life cycle is unusual in invertebrates but occurs in all millipedes. After 2-4 weeks the protonymph moults into a first instar nymph which has a mouth, eyes & legs. After this it moults regularly as it grows in size. adding new body segments and more legs each time this occurs.
The picture above shows two millipede eggs, a protonymph (on the right of the eggs) and a 'true' baby millipede (top left) which will have moulted a couple of times at least since the protonymph stage. You can see that even after a couple of moults the babies are still really tiny! It is at this stage that they can be found on the surface of the substrate in their enclosure, whereas before this they would remain underground.
The picture below show the size difference between a two-year old African giant millipede compared to the baby on the left of the picture above!!
As you can see they grow a lot in two years but even this one at 16cm is still very small compared to the adults at 25 - 35cm!
Children and adults alike love to handle giant millipedes because their bristly legs feel absolutely amazing, a bit like a live hairbrush!