Why do bees die after stinging you but not after stinging each other?

The honeybee's sting is barbed like a harpoon. Insect shells are thin and flexible enough that the barbs pull back out, so a bee fighting a wasp stings repeatedly and survives; mammal skin is elastic and grips the barbs, so pulling away tears the sting, venom sac and part of the abdomen out of the bee, which then dies.

This is only worth having because a honeybee colony is effectively one organism. A worker cannot reproduce, so losing her costs the hive very little compared with driving off a bear - and the detached sting keeps pumping venom for up to a minute after she has gone, which a survivable sting would not. It is a defence evolved against large animals raiding honey.

The advice on removing one is now the opposite of the traditional version. Scraping rather than pinching was long recommended to avoid squeezing more venom in, but the trials found what matters is speed: get it out immediately by whatever method. Only honeybees die this way - wasps, hornets and bumblebees have smooth stings and can sting as often as they like.