High-speed video reveals how honey bee stingers pump venom

Workers of Apis mellifera leave their stingers embedded and those detached stingers continue to pump venom autonomously via a previously unobserved double-piston mechanism. The venom canal is formed by a widening stylet and two sliding lancets whose attached valves change shape as they reciprocate: they balloon like parachutes on the downstroke to form a seal and apply downward pressure that expels venom, collapse on the upstroke, and deform as they meet to pass one another. Because the two valves pump in opposite phases and create tight seals, the system produces a continuous forward flow and minimizes backflow, explaining how venom delivery persists after the bee flies away.

The discovery rests on high-speed color videography and stereomicroscopy of freshly excised stingers partially inserted into gel, with frame-by-frame tracking of semi-translucent structures, supported by flow-visualization tests and micro-CT-informed 3D-printed scaled models that replicated the kinematics. Replication required highly elastic, low-friction polymer valves, highlighting material properties as critical to the mechanism; capillary forces at this small scale remain to be assessed. The compact, autonomous double-piston design suggests practical bioinspired uses for microneedles, tissue-penetrating devices, and microfluidic or implantable pumps.