Swatting a honey bee rarely ends a sting. The insect leaves its barbed weapon in the skin, and the stinger carries on injecting venom for more than a minute without any help. Researchers in Australia have now caught on camera the machinery that makes this possible, and it turns out to be an unusual pump with two collapsible pistons.
The study, which appears in PNAS, was led by Fiorella Ramirez-Esquivel, a biologist at Sydney’s Macquarie University, working with a team from UNSW. Scientists had sketched the stinger’s internal valves as far back as 1910, yet no one had seen them in motion. The team let bees sting a transparent gel designed to behave like human skin and recorded the detached stingers at 300 frames per second.
Inside the tiny venom chamber sit two valves, each fixed to one of the needle-like lancets that slide back and forth like a reciprocating saw. On the way down a valve flares open like a parachute, seals against the walls and drives venom out. On the way back it folds up like an umbrella so the chamber can refill. Because the two valves travel in opposite directions, they also have to squeeze past each other mid-stroke, which they manage by changing shape again. The result is a steady, uninterrupted flow.
“The unique geometry of the valves is the key,” Ramirez-Esquivel said. To test the idea, the group turned micro-CT scans into an enlarged 3D-printed model built from rigid and flexible plastics, and it reproduced the pumping cycle. The filming alone took hundreds of hours, during which the lead author says she was stung only once.
Losing its stinger can cost the bee its life, but the design could live on in engineering. The authors suggest it as a template for compact micropumps in microfluidics, drug delivery and minimally invasive medical devices.
