The dreaded red fire ant is a real pain. But it is far from the biggest pain in the insect world.
This invasive species — which now infests parts of Queensland and New South Wales and is subject to a national eradication program — gets its name from its sting, which apparently burns like fire.
On the pain scale that measures insect bites and stings, from mild tingling to bullet-wound agony, it rates a relatively modest 1.2, however.
The scale reaches 4.0 — the sting of a giant wasp earning the description “blinding, fierce, shockingly electric” by the scientist who developed the index.
That scientist was American entomologist Justin Orville Schmidt, who created the index by stinging himself with some of the world’s most fearsome insects.
The director of the Australian National Insect Collection, CSIRO entomologist David Yeates, said the red imported fire ant’s low Schmidt index rating did not tell the full story of this exotic menace.
“Red fire ants are an invasive species that over the past decade or so got into South-East Queensland and have spread a bit further than I think the eradication team would have liked,” Dr Yeates said.
“Wherever it occurs it can cause a lot of disturbance to humans, it forms in big colonies and can displace other native ants and invertebrates.
“When they sting you, you can get stings from many insects at once. Also, if the insect that stings you lives in colonies, like the fire ant, they send an alarm pheromone and that tells all the other members of the nest there’s an intruder and to attack as well.”
The red fire ant has marched south but has not been recorded in Victoria yet. There is no shortage of common insects which have a Schmidt index pain rating higher than the fire ant’s score of 1.2, however.
Even the humble honey bee scores 2.0.
Dr Schmidt, who died this year (not from an insect sting), developed his index in 1980.
It was a case of a scientist taking commitment to his field to the nth degree, Dr Yeates said.
“Over the course of his career, [Dr Schmidt] deliberately had himself stung by lots of ants, bees and wasps.
“He wrote notes down after he was stung, describing the pain and giving it a rating of zero to four.
“I suspect sometimes, when Justin was getting stung, he wished he hadn’t started on the whole venture, but he became quite a well-known scientist through his pain index.”
While the Schmidt index (see below) includes bites, those at the upper end of the spectrum tend to be delivered by the insects’ stingers rather than by their fierce-looking mandibles, Dr Yeates explained.
“All ants have mandibles so they can bite you with effectively their insect teeth,” he said.
“The real sting is at the other end of the body. It’s really a modified egg-laying ovipositor modified into a stinging organ.
“Generally, the worker bees or ants are sterile females with this modified ovipositor and will sting you quite happily.
“Bull ants have very big jaws and they use them to hang on while they sting multiple times with their stinger.”
The index is not necessarily an indicator of toxicity. There isn’t always a correlation between pain and actual harm, according to Invertebrates Australia founder Kate Umbers from Western Sydney University’s School of Science.
A spider wasp may have a more painful sting but be less likely to cause an anaphylactic shock in its victim than a bee or bull ant, for example.
“The pain may not have been backed up by something in order for that organism to deter its predators. They don’t have to kill us to be protected,” Dr Umbers said.
“Being super, super painful is probably enough to convince people not to mess with large wasps.
“Wasps and bees that want to deter humans and other mammals from taking their stuff, such as honey, may have an evolutionary correlation with their venom types and harm.
“But you have to remember, Insects are ancient — they are 458 million years old — we are just 2 million. So the more than 450 million years of evolution before we showed up are probably more important in determining toxicity.”
The index of pain
The Schmidt index is somewhat subjective, and larger specimens of an insect type may deliver a more painful sting than smaller ones.
The index applies to insects only, so other stinging invertebrates, like centipedes, scorpions and spiders, do not get a Schmidt index rating.
Dr Yeates offered these ratings for some of Australia’s most encountered things that sting. The garden-variety black house ant rates a 0.1.
0.5 – meat ant
These Australian natives do not sting but will bite.
0.5 – green tree ant
Another Australian native which does not have a sting as such but can bite and spray the wound with formic acid for extra “fun”.
1.2 – red fire ant
An unwelcome import which delivers a “sharp, mildly alarming” sting. Repeated stinging feels like your skin is burning.
1.5 – green head ant
Its stinger packs a punch for its small size.
2.0 – European honey bee
Many Australians can attest to the pain of a bee sting.
2.5 – bumblebee
Can sting more than once and has more venom than a honey bee.
2.5 – European wasp
An unpleasant character with a painful sting and a bad attitude. Very aggressive and will attack in large numbers.
2.5 – potter wasp, paper wasp, mud dauber wasp
These native wasp species have a painful sting but are rarely aggressive towards people.
3.0 – bull ants
Fearsome looking and aggressive. In addition to pain, their venom causes anaphylaxis in many people. The jack jumper ant is a variety of bull ant.
4.0 – spider wasps
Their venom is designed to incapacitate large spiders. Dr Schmidt described the sting of the American tarantula hawk — a type of spider wasp — as like a “running hair dryer dropped into your bubble bath”.
