Nothing Impedes Millipedes

Today's rain here in Canberra has inevitably driven a few small black cylinders on legs to come pottering across the floor, seeking refuge from flooded shelters. They are millipedes; in particular they are descendants of Portuguese animals which somehow turned up in South Australia some 60 years ago, and have since spread across southern Australia. As far as I can tell they have no negative impact on the natural world, so I'm happy just to put them back out to take their chances with the weather (better that than being inadvertently trodden on). Aside from anything else I'm in awe of their heritage, which goes back unimaginably further than either Portugal or Australia can understand. 

Millipede ancestors wandered and munched their way through the very first tiny land forests, some 430 million years ago... (I'll pause while your brain - and mine - stops reeling.) As far as we know, the first entirely land-based animals were millipedes, and the group has coped with the climatic and geological horrors that have since repeatedly wiped out the majority of life on earth; their grandchildren can cope with a bit of rain. While millipedes are harmless, we may like to ponder that 130 million years after the first ones, Arthropleura, at 2.5 metres long, became the largest land invertebrate ever to live.

Portuguese Millipede, Ommatoiulus moreleti.

This picture tells us a few things (not least my limitations as photographer, but that's not what I meant). Certainly millipedes have lots of legs, but nowhere near 1000 (which is the translation of millipede). The number of legs varies from a few dozen to a few hundred in different species. We can also see that the pairs of legs are themselves in pairs; this is because each body segment has two pairs. (A careful look reveals actually that this doesn't apply to the first few segments.) The next picture perhaps shows better why this is so.

Millipede, Mt Kupe, western Cameroon.

The alternating colours make it easier to see that each segment comprises two segments, fused together - each brings with it its own pair of legs. This is also typical millipede defense behaviour, curling up to protect its vulnerable undersides. 

A similar pattern can be seen in this beauty from outside the Gomantong Caves in Sabah.

Despite being hard, the carapace isn't waterproof. Like those of other arthropods, it's made of chitin, that tough flexible sugar-based armour that makes arthropods so successful, but they don't have a waxy waterproofing coating so must stay in moist conditions. (Evidently not too moist though, as my kitchen refugees attest!)

You may have noticed that with the last picture I stopped offering names; sorry to let you down, but the fact is that there are 10,000 known millipede species, about the same number of species as there are of birds in the world. In fact they form their own Class, as do birds, with all the diversity that implies. The rest of the pictures here illustrate something of that diversity, and ubiquity.

Machu Picchu, Peru. As far as I can tell (the front end is a bit shadowy)
this one has 60-70 segments, ie 240-280 legs.

Machuguenga, Peruvian Amazonia.
A very different body pattern; this species, and the next
two, have apparently only 18 segments.
This (I suggest cautiously) puts them in the Order Polydesmida.

Batang Ai National Park, Sarawak.

Mt Cameroon, Cameroon.

Ecuadorian Amazonia.
The sensory antennae are obvious here, and in the next picture.

South coast New South Wales.

Crocker Range National Park, Sabah.

Having referred to them as harmless - nearly all eat decaying vegetable matter, and defend themselves solely by emitting nasty-smelling chemicals - I might get an argument from the Victorian Railways. Earlier this year Portugese Millipedes were moving in such numbers that they covered the rails, preventing signal activation.

I'm betting that millipedes will be round long after trains have become an archaeological artefact.