Australia has roughly 4,000 species of ants and some of these are very distinctive - for example, the tree-nesting green ants seen throughout the Wet Tropics and northern Australia. Others are very tiny, making a nuisance of themselves once they get into homes. At the other end of the size spectrum are the aggressive bull ants - a species two-to-three centimetres in length whose bite is not quickly forgotten.
There is even an ant species that has a symbiotic relationship with an epiphytic plant called an ant-house plant (Myrmecodia beccarii). The ant provides a physical defence against plant eating invaders and the plant provides housing and, possibly, food for the ant. A third species is also part of this symbiosis. The gorgeous Apollo jewel butterfly lays a single egg on the top of each anthouse plant. The ants carry the hatched larvae (a caterpillar) inside the plant where the larvae eats out chambers inside the plant, providing more space for the ants. The caterpillar also produces droppings which are nourishing for the ants while the ants protect the caterpillar from predators.
Green Ants (Oecophylla smaragdina) are extremely common in far north Queensland and build large nests in trees by sticking the leaves at the end of branches together to create a sort of globular home. They clamber all over the tree containing their nest and serve to protect it from invaders. These ants are often found in fruit trees. When the unsuspecting person tries to help themselves to some tasty fruit to eat, the aggressive green ants drop down on them and start biting (not stinging). Their bite is not very painful but several ants attacking simultaneously can be rather uncomfortable because after biting they spray formic acid into the wound.