Jack jumpers (Myrmecia pilosula) are small, black and orange ants with extremely keen eyesight and an unusual ability to jump. This tiny creature is considered one of the most dangerous ants in the world – and, indeed, one of the most dangerous animal in Australia! In Tasmania, the death toll from the jack jumper’s sting is about one person every four years – greater than the toll inflicted by sharks or by the most poisonous of snakes or spiders.
They are named after the ‘jumping-jack firecracker’ because of their tendency to jump aggressively towards potential threats to themselves or their nests, and to follow up with multiple painful, fiery stings. The ant’s fierce-looking, toothed jaws are ideal for holding insect prey in place while using the stinger at the end of its abdomen to jab its victim. Jack jumpers are so very dangerous because the venom in their stings is one of the most powerful in the insect world; about 3 per cent of Tasmanians (some 14,000 people) are at risk of anaphylactic shock if stung.
While jack jumpers are common in the bush, their preference for disturbed, sparsely-vegetated and stony ground allows them to colonise roadsides, pathways and heavily-grazed paddocks. For the same reasons, they can also be common in recently-established suburbs. Nests are typically found under logs and rocks and can often be spotted from the mounds of gravel that mark the entrance holes.
Not one single ant species, but a complex of seven superficially very similar species, jack jumpers hold a key position in native ecosystems. Despite their notoriety, their nest-building improves soil structure, while their predatory and competitive behavior with other insects and invertebrates helps to selectively enhance plant growth. They are also a food source for other animals. The most important predator of jack jumpers is the echidna, which – unfortunately for people – avoids disturbed ground and suburban areas.