Most cases of human reaction to ant stings in Australia involve so-called "jack-jumpers". These are small black bulldog ants about 10 to 14 mm in length with bright orange jaws, antennae and legs.
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They occur in eastern NSW, Victoria, Tasmania and southwest WA and are easily recognised by their habit of hopping about aggressively when disturbed. They are truly ants with attitude.
They are considered by experts to be perhaps the most venomous to humans of all world ants, partly because, unlike other known "nasties", they have broad contact with human populations, and stinging is not uncommon.
Their workers hunt other insects which are stung to death, quickly immobilised and carried or dragged back to the ant nests as food. This is the function of the venom, and the fact that humans are sensitive is simply a side-issue.
Sting reactions in humans range from local swelling and quite intense pain to severe anaphylactic shock and unconsciousness. On rare occasions it can be lethal. The fatality statistics are similar to those for honey-bee stings. Allergists believe that some cases of bush-walkers and others found alone and dead in the bush could be due to jack-jumper stings.
Jack-jumpers are abundant in recreational areas like the Snowy Mountains, the Australian and Tasmanian alps and the Grampians in Victoria. They occur in Sydney, Melbourne and especially in Canberra, Armidale, Adelaide and Hobart. Their nests in the soil are usually marked by mounds, which are often decorated with gum nuts or gravel.
Allergists maintain a national register of people who have experienced symptoms, and there are many who must take precautions to avoid or treat future stings.
Two jack-jumper species are common in Canberra and surrounding grasslands, in parks, gardens and nature-strips. They are scientifically very interesting because one is a natural hybrid between two other species, and the other is the only animal "higher' than a nematode worm to have only a single pair of chromosomes.
There are many stories of sting experiences. One woman in NSW is so sensitive that even going near a nest will cause a reaction, even if she isn't stung. Another woman in Victoria stopped to help at a roadside car accident, but after she stepped on a Jumper nest, it was her who was taken to hospital.
Response by: Dr Robert Taylor, Adjunct Professor, ANU College of Medicine, Biology and Environment
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