The bullet ant (Paraponera clavata) gets its name from the shot of intense pain it delivers with its venom-filled sting. The recipient experiences its agonising effects for the next 12 - 24 hours.

Living in the South American rainforest and growing to around an inch (2.54cm) long, most of us are capable of keeping out of its way.

Level four you don’t want to know

However entomologist Dr Justin Schmidt has got close enough to this vicious ant in attack mode to rate its sting as the most painful in the world.

He describes the experience as: “Pure, intense, brilliant pain. Like walking over flaming charcoal with a three inch nail embedded in your heel.”

Dr Schmidt, from the Southwestern Biological Institute in Arizona, US, is no stranger to the pain inflicted by insects. He reckons he’s been stung more than a thousand times by 150 different species – mainly accidentally, but occasionally on purpose.

As the man behind the Schmidt Sting Pain Index – which rates the pain caused by the stings of different hymenoptera (a group of insects that includes wasps, bees and ants) – leaving well alone has never been an option.

It lists pain on a scale from one to four and unsurprisingly the bullet ant tops the charts.

Level 4: bullet ant, tarantula hawk wasp

bullet ant, tarantula hawk wasp Level 3: paper wasp, harvester ant

paper wasp, harvester ant Level 2: honey bee, yellow jacket wasp, bald-faced hornet

honey bee, yellow jacket wasp, bald-faced hornet Level 1.5: bullhorn acacia ant

bullhorn acacia ant Level 1: fire ant, sweat bee

“Level four you don’t want to know,” explains Dr Schmidt.

“The pain is so immediate and intense that it shuts down all illusions of life as normal. Imagine sticking a finger in a 240 volt electrical socket.”

Rated just beneath the bullet ant for the excruciating, but shorter-lasting nature of its sting is another tiny terror, the tarantula hawk wasp. Females use their venom to paralyse much larger tarantulas to feed to their offspring.

“Blinding, fierce, shockingly electric. A running hair drier has just been dropped into your bubble bath,” is the description given by Dr Schmidt.

The pain inflicted by the humble honey bee comes bang in the middle of the scale at a pain level of two.

Dr Schmidt has experienced most of the stings while collecting live nests in the field, but his interest in this form of defence mechanism was first piqued when he was bitten after sitting on an ant hill as a child.

You probably can make an argument I am crazy, but I enjoy what I do

Since then he has scientifically quantified the pain he has felt through his index, which was first published in the 1980s before being revised in 1990 to include 78 species.

He has also studied the chemistry behind the pain, as well as why and how insects use venom against predators.

“More pain receives more attention and is therefore a better defence,” Dr Schmidt says.

“Also it tends to allow bigger aggregations to form, and enabled the evolution of sociality in many groups.

“It also allowed the use of resources that otherwise would be risky, such as flowers during broad daylight.”

Dr Schmidt is regularly called upon to use his expertise to advise on the ferocity or otherwise of wasps, bees and ants around the world. He is also working on his latest version of the pain index in which he hopes to list many more species.

After more than 30 years on the frontline of his field in stinging insects, Dr Schmidt says there still remains some reportedly fierce species he would like the chance to be hurt by. They include wasps in eastern Peru and tree-living ants in the Congo.

"I don’t consider myself all that tough," he says.

"Crazy? Well that’s in the eye of the beholder. You probably can make an argument that I am crazy, but I enjoy what I do."

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