This is most likely a Scolopendrid centipede. Centipedes can range from a couple of millimetres to 30cm. Found worldwide, except for polar regions, they eat insects and other tasty morsels. Big centipedes can even eat geckos! This one was found on the back step of my house in Cairns. Like all centipedes, this one has venom, and although not lethal, can pack an extremely painful bite. It feels like being stabbed with a red hot needle! You can ask my Aunty!