Early in his career, Justin Schmidt realized he had a problem.
Schmidt, a budding entomologist, and his zoologist wife had just returned to the University of Georgia from a trip around the country.
They'd been collecting different species of harvester ants, "nasty stinging insects whose venom chemistry was unknown," as he describes them in his fascinating new book, "The Sting of the Wild."
To learn the details of the venom for his dissertation, they had to analyze incredibly large numbers of the creatures, which meant getting up close and personal with them.

The Sting of the Wild/Johns Hopkins University Press

Debbie, Schmidt's wife, describes her first harvester sting in the book as a "deep ripping and tearing pain, as if someone were reaching below the skin and ripping muscles and tendons; except the ripping continued with each crescendo of pain."

After collecting buckets of the creatures, the plan was to analyze them and compare the venoms from different specimens. To assess venom, Schmidt needed to evaluate both toxicity and pain. Toxicity was straightforward — already existing measures could be used. But there was no existing scale to measure the pain of insect stings.

Thus was born the "Schmidt Pain Scale for Stinging Insects." It was a four-point system, anchored by the well-known sting of a honey bee (rating a two), something people all over the world could be familiar with. To go up or down a full point, a sting had to be discernably more or less painful than the stings on another level. Half points could be used for pricks that fell somewhere between levels.

Over the years, Schmidt added new species to the list. He mostly didn't try to get stung. It just happened, more than 1,000 times, from at least 83 different species that have been evaluated on the index.

We've picked out insects that will illustrate the full scope of the scale, including a few that demonstrate the worst of the worst:

Red fire ant

Scientific name: Solenopsis invicta
Range: Native to South America
Description: "Sharp, sudden, mildly alarming. Like walking across a shag carpet and reaching for the light switch."
Pain level: 1

Western cicada killer

Scientific name: Sphecius grandis
Range: North America
Description: "Pain at first sight. Like poison oak, the more your rub, the worse it gets."
Pain level: 1.5

Western honey bee

Scientific name: Apis mellifera
Range: Native to Africa and Europe
Description: "Burning, corrosive, but you can handle it. A flaming match head lands on your arm and is quenched first with lye and then sulfuric acid."
Pain level: 2

Western yellowjacket

Scientific name: Vespula pensylvanica
Range: North America
Description: "Hot and smoky, almost irreverent. Imagine W.C. Fields extinguishing a cigar on your tongue."
Pain level: 2

Fierce black polybia wasp

Scientific name: Polybia simillima
Range: Central America
Description: "A ritual gone wrong, satanic. The gas lamp in the old church explodes in your face when you light it."
Pain level: 2.5

Velvet ant (technically a wasp)

Scientific name: Dasymutilla klugii
Range: North America
Description: "Explosive and long lasting, you sound insane as you scream. Hot oil from the deep frying spilling over your entire hand."
Pain level: 3

Florida harvester ant

Scientific name: Pogonomyrmex badius
Range: North America
Description: "Bold and unrelenting. Somebody is using a power drill to excavate your ingrown toenail."
Pain level: 3

Tarantula hawk

Scientific name: Pepsis spp.
Range: North America, Central America, and South America
Description: "Blinding, fierce, shockingly electric. A running hair dryer has just been dropped into your bubble bath."
Pain level: 4

Bullet ant

Scientific name: Paraponera clavata
Range: Central America and South America
Description: "Pure, intense, brilliant pain. Like walking over a flaming charcoal with a 3-inch nail embedded in your heel."
Pain level: 4

Warrior (or armadillo) wasp

Scientific name: Synoeca septentrionalis
Range: Central America and South America
Description: "Torture. You are chained in the flow of an active volcano. Why did I start this list?"
Pain level: 4

Source