Centipedes form the class Chilopoda, which are described in texts as land dwelling arthropods which are flattened dorsoventrally, with a distinct head and numerous body segments.
If you are scared of centipedes, be grateful that you don't live in some tropical countries, where they can grow to 30 centimetres. The largest Australian centipede I have seen was around half of that length, although most I encounter in the garden are much smaller.
Close contact with centipedes may challenge the idea that all of natures biodiversity is valuable, that we should not be only concerned with the "furry, cuddly" bits of nature. They seem to combine the squirminess of worms, the multi-legged scurrying of millipedes and the shuddering fear of fang and poison which spiders have for many people. However centipedes play a very useful role in pest control, and buy and large keep out of your way.
Centipedes are often found sheltering if you move pots, timber, corrugated iron or other debris. They can also be found under leaf litter in natural settings or actually in the soil, when digging.
A typical centipede has short stout legs, a long trunk with segments, like a millipede, and a broad "flattened out" appearance. Centipede may mean "hundred legged", but most centipedes have around 35 pairs of legs. The range of legs goes from about 15 pairs in the Scutigera to 173 pairs in the geophilids.
There is also the "house centipede" or Allothereua maculata, which has longer, delicate legs, a sort of "feathery" appearance and is sometimes known as the "house centipede". If this beasty is found in houses more than any other centipede, it is probably only because they are adapted to climbing, rather than restricted to terrestrial (ground) habitats. They greyish colouring of the house centipede is a disguise for living under bark and in litter, whereas the regular centipede is either a brown-orange or a greenish colour, for leaf litter and soil dwelling.
The Allothereua maculata, as far as I now, is totally harmless to humans. Other centipedes can cause a nasty reaction. They use poison to attack their prey, injected by modified appendages on the first body segment (all the other body segments have legs, except the last two. Centipedes have only one pair of legs per body segment, unlike the millipede, which has several pair.
Having many legs doesn't seem to slow centipedes down at all, despite the coordination problem it must present, and they can run along very fast.
Most centipedes lay eggs in the ground, and the young hatch with only seven segments. I have discovered caches of eggs and newly hatched young, which seemed to be capable of very active movement and hunting right from the start. They shed their exoskeleton frequently as they grow and add segments along the way, ending up with at least seventeen segments.
Centipedes are carnivorous and feed on soft bodied insects. They will control cockroaches, silverfish, slugs, caterpillars, mites and lice. I have noticed that they particularly like to find a cache of slug or snail eggs. They will also eat earthworms. Because they live under bark or litter or in the ground, eyesight is poor (they have more than one pair of eyes) and they rely on feel quite heavily. Centipedes also shun light, and are mainly nocturnal. They do not have the waxy, waterproof cuticle that insects have either, which forces they to remain in more humid environments, such as under stones and logs. In droughts or very cold weather they sneak into crevices in the ground to hide and wait for better conditions.
It is not easy or necessarily desirable to encourage centipedes into the garden. However I practice tolerance of small animals such as centipedes. I recognise the good they can do in the garden and their greater role in the whole "scheme of things" which is the natural ecosystem. Most people would suffer very little if bitten, perhaps a painful swelling like a bee or wasp sting, although there is always the possibility of an allergic reaction, or of a child, ill or elderly person responding badly, or a shock reaction from someone's fear of centipedes, rather than the toxic response. Like many pests including spiders, earwigs etc, they will be most noticeable after major disturbance, such as after vegetation clearance or in a new building site or development, where they are actively seeking shelter.
Sensible precautions are to wear gloves when lifting rubbish or trowelling in areas where they are known to be, to remove them to the "wild areas" of the garden when they are found, or to give them wide berth and simply leave them alone.
Centipedes, spiders and other creatures can be removed from the house in the following way. Place a wide mouthed jar over the creature, whether it be on the floor or on a wall. Slip a piece of paper or cardboard under the rim, to cover the mouth. Try not to squish the limbs of the animal in the process. Up end the jar, carry it outside and release the creature. If you have a major problem with them, screw on a lid and take them off to the local reserve of bushland.