Honey bees are known to leave their stingers embedded in tender flesh once they sting you and fly away. Scientists have now determined that the stinger is able to continue pumping venom into its unfortunate victim even after the bee flies away, thanks to a unique double-piston pump-like mechanism, according to a new paper published in the Proceedings of the National Academy of Sciences.

Different species have evolved different mechanisms for delivering venom, which involves piercing the skin and then pumping venom from a gland or reservoir. Spiders, for instance, have muscles surrounding their venom glands, which contract and eject venom through hollow fangs. Bees, wasps, and ants deliver venom via their stingers, either by contracting muscles around the venom reservoir or through stiff elements called lancets working together to pump venom.

Honey bees (Apis mellifera) add a unique feature: Worker bees fly away after inserting their stingers in the target, leaving the stinger behind. The stinger continues to penetrate the tissue and pump venom on its own, a rare phenomenon known as autotomy. A honey bee’s stinger has three main interlocking elements that form the venom canal: a stylet that widens to form the main pumping chamber and two sharp-tipped lancets that slide back and forth, piercing the tissue and pumping venom into the target. But the precise mechanism by which the pumping action is achieved has never been directly observed.

The authors of this latest paper sought to capture the venom-pumping kinematics of honey bee stingers in order to identify the underlying biomechanics. They collected live worker bees and removed the stingers with forceps just prior to filming. Then they partially inserted those stingers into blocks of artificial gel and captured the pumping action using stereomicroscopy and high-speed color videography. This was followed by a frame-by-frame analysis to better track the movement, which is visible because the structures are semi-translucent.

That footage revealed that the valves attached to each lancet—both of which sit inside the venom pumping chamber—change shape during pumping as they slide back and forth. They inflate like a parachute on the downstroke, creating a seal via a piston-like action that applies downward pressure in the chamber to push out the venom. They deflate on the upstroke. And the valves change their shape again when they meet in the middle in order to push past each other.

“The unique geometry of the valves is the key; they act as collapsible pistons and—by pumping in opposite directions—they’re able to deliver a continuous flow of venom,” said co-author Fiorella Ramirez-Esquivel of Macquarie University. “The double piston design adds complexity, but it’s the key to the stinger being able to deliver venom continuously in a compact, autonomous unit.” The dual motion also minimizes backflow.

Those results were consistent with the authors’ preliminary flow visualization experiments. To verify the initial findings, the team took micro-CT scans and used that data to create a 3D-printed scaled prototype model to mimic the observed pumping behavior. This pumping motion, too, was filmed and analyzed frame by frame. The artificial pumping model showed the same pumping kinematics as the biological stingers.

Future research may focus on a closer examination of the material properties of the valves, since the team’s artificial polymer valve shows extremely high elasticity is key to replicating the necessary valve deformations, along with low friction between the valves. It would also be useful to investigate whether capillary action plays a role, given the small size of the venom-pumping elements. Capillary action could help draw venom into the venom canal, or, alternatively, the venom may need to counter capillary action that draws fluid up from the tissue.

Prior research has used bee stinger structure as inspiration for the design of microneedles, tissue transport devices, and drilling devices. The authors believe their own work will eventually find similar medical and microfluidic applications, such as for artificial pumps.

PNAS, 2026. DOI: 10.1073/pnas.2603916123  (About DOIs).