Firstly they are a general nuisance but they may present a health risk. For instance, they mechanically carrying disease organisms on their bodies. They also carry it in their digestive tract that can cause dysentery, smallpox, and a variety of pathogenic bacteria, including salmonella.
We have many different species in Australia, the most commonly known is the carpenter ant, bull, green-headed, sugar, jumper, meat, and green tree. It’s the green ants that can actually inject venom. The jumper ant can cause a severe allergic reaction. Other species such as the meat and the green tree don’t sting but bite and spray formic acid into the wound. Then we have those pesky black ones that make mounds and nests in the soil. You can find these in timber, under pavers, in wall cavities, around skirting boards and in roof voids.