The Schmidt Sting Pain Index is a pain scale created by American entomologist Dr. Justin O. Schmidt. It rates the relative pain caused by the stings of various Hymenoptera (ants, bees, and wasps). Schmidt personally experienced stings from over 150 species and documented his observations with vivid, often humorous descriptions. The scale ranges from 1 (mild) to 4 (extremely painful), with some insects rated at 4+.

The index has four main levels (1 through 4), with some insects receiving decimal ratings (e.g., 1.5, 2.5). Level 1 represents mild, transient pain. Level 2 indicates moderate pain similar to a honey bee sting. Level 3 describes severe, burning pain. Level 4 is reserved for excruciatingly painful stings that can incapacitate the victim temporarily. The Bullet Ant is rated 4.0+ — the highest on the scale.

The Bullet Ant (Paraponera clavata) is rated 4.0+ and is widely considered the most painful sting in the insect world. Schmidt described it as "Pure, intense, brilliant pain. Like walking over flaming charcoal with a 3-inch rusty nail grinding into your heel." The pain can last 12–24 hours. The Tarantula Hawk and Warrior Wasp also score a solid 4.0, making them among the most painful stings known.

Dr. Schmidt personally experienced most stings during his field research as an entomologist. He didn't deliberately provoke stings for the index; rather, he documented stings that occurred naturally during his work handling and studying Hymenoptera. Over decades of research, he accumulated detailed notes on over 150 species, creating the index from first-hand experience. His dedication earned him the Ig Nobel Prize in Biology in 2015.

While subjective by nature, the Schmidt Sting Pain Index is widely respected in entomology as a consistent comparative framework. Schmidt applied standardized criteria: pain intensity, duration, and character. His detailed, evocative descriptions help both scientists and the public understand the relative severity of different stings. It remains the most comprehensive and cited pain scale for insect stings available.

According to Schmidt, a Bullet Ant sting produces "pure, intense, brilliant pain" comparable to walking over burning charcoal with a rusty nail in your heel. The pain comes in waves, lasting 12 to 24 hours. Victims often experience uncontrollable shaking, temporary paralysis of the affected limb, and profuse sweating. Indigenous tribes in South America use Bullet Ants in initiation rituals, where young men must endure dozens of stings simultaneously.

The Tarantula Hawk sting is rated 4.0 but the intense pain is relatively short-lived — usually 3 to 5 minutes. However, those minutes are described as absolutely excruciating, with Schmidt comparing it to "a running hair dryer dropped into your bubble bath." Despite the brief duration, the instantaneous, debilitating pain makes it one of the most feared stings.

The index covers the order Hymenoptera, which includes bees, wasps, ants, and sawflies. Most entries are ants, bees, and wasps. Notably, some ants (like the Bullet Ant and Harvester Ants) rank among the most painful. Velvet Ants — which are actually wingless wasps, not true ants — also feature prominently at level 3. The diversity highlights how sting potency evolved independently across different Hymenoptera lineages.