If you’ve ever been stung by a honeybee, you might know they have a special trick: they insert the stinger into your skin and leave it behind. As they fly away, the needle-like appendage keeps stinging you.

Losing the stinger can kill the bee by damaging its internal organs, so they don’t do it lightly. However, it means that even if the bee is crushed or brushed off, the stinger will continue to do its job – defending the hive. In fact, it takes over a minute to finish pumping after it enters the skin.

The stinger is effectively a fully autonomous micro-pump. But how does it work all on its own?

Most venomous animals store venom in a venom sac – more or less a very unpleasant water balloon. Circular muscles around this balloon squeeze and release the venom. But scientists have known for a while that honeybees are equipped with something different.

A honeybee’s venom sac empties into a pumping chamber, which contains little pumping elements called valves. This was illustrated as early as 1910 but we’ve........

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