Here's a short video of one washing its pincers:
Christine did a bit of researching, and while they appear to come in a variety of colors, the huge yellow mandibles point toward these being Jack Jumper ants, also known as a Hopper or Skipper ants, a type of bull ant from the primitive genus Myrmecia, which is found only in Australia (well, one of the ninety or so species is found in New Caledonia):
The Jack Jumper Ant is a large species of Bulldog Ant. They have a jumping motion when disturbed which gives them their common name. The workers are black with yellow mandibles, antennae, and lower parts of the legs. The head is slightly broader than it is long and mandibles are slightly shorter than the head. The mandibles have four large sharp teeth with a smaller tooth in between each large one. The queen is similar in colour to the workers but is larger and more robust.
That pretty much describes the guy in the photo above, although the "black" in this case is more bluish, and the legs aren't quite as yellow as the photos I'm seeing, but nature is not that consistent.
I looked back at the several videos I took of them, and I even saw one jumping. (It happens very quick in this short video.)
The special thing about these ants is their sting. They don't bite, they sting, like wasps (which ants and bees are related to). And it's a very powerful sting:
A program to desensitise people to the potentially fatal jack jumper ant in Tasmania has been declared a success.
At less than a centimetre long with bright orange pincers, the jack jumper ant may be small but its sting can be deadly.
Allergic reactions can be more severe than those to bee stings, ranging from a rash and swelling, to unconsciousness and even death.
Of course. It's Australia. More:
In areas where Jack Jumper ants are common, population surveys have shown that between 2 and 3 per cent of people have had generalised allergic reactions, and in around half of these people the reactions can be life threatening. Deaths from Jack Jumper ant stings and anaphylaxis have occurred in Australia, with several recorded cases in recent years. Since allergy as a cause of death can be difficult to detect at post mortem, it is conceivable that deaths due to sting allergy are under reported.
An extra fact:
The jack jumper ant genome is contained on a single pair of chromosomes (males have just one chromosome as they are haploid), the lowest number known (or even possible) for any animal.
Lots more photos at Ants Down Under.