A high-speed video shows how a bee sting pumps venom

"The unique geometry of the valves is the key; they act as retractable pistons" to deliver the poison, one of the authors wrote.

Once the bees have stung you and flown away, they leave their stingers in the tender flesh. According to a new paper published in the Proceedings of the National Academy of Sciences, scientists have now concluded that the stinger can continue to pump venom into its hapless victim even after the bee has taken off, thanks to a unique double piston-like pump mechanism.

Different species have developed different mechanisms for venom delivery, which involve piercing the skin and then pumping the venom from a gland or reservoir. For example, spiders have muscles that surround their venom glands, which contract and expel the venom through their fangs. Bees, wasps, and ants deliver venom through their stings, either by contracting muscles around the venom reservoir or through stiff elements called lancets that work together to pump out the venom.

Honey bees (Apis mellifera) add a unique feature: after inserting their stinger into a target, the worker bees fly away and leave the stinger behind. The sting continues to penetrate the tissue and pump out the venom on its own, a rare phenomenon known as autotomy. A bee stinger has three main interlocking elements that make up the venom channel: a stinger that widens to form the main pumping chamber, and two pointed lancets that slide back and forth to pierce the tissue and pump the venom into the target. But the exact mechanism by which the pumping action is achieved has never been directly observed.

The authors of this recent paper sought to uncover the kinematics of bee sting venom pumping in order to identify the underlying biomechanics. They collected live worker bees and removed the stingers with forceps just before filming. They were then partially embedded in artificial gel blocks and recorded the pumping action using a stereomicroscope and high-speed color video recording. A frame-by-frame analysis was then performed to better track the motion, which is visible because the structures are semi-transparent.

The video showed that the valves attached to each lancet—both of which are inside the venom pumping chamber—deform and slide back and forth during pumping. They inflate like a parachute on the downstroke, creating a seal through a piston-like action that applies downward pressure to the chamber to expel the venom. They blow on rising. And the valves change shape again when they meet in the middle to pass each other.

Fiorella Ramirez-Esquivel of Macquarie University, one of the authors of the paper, said: "The unique geometry of the valves is the key; they act as retractable pistons and - by pumping in opposite directions - can create a continuous flow of venom." The dual-piston design adds complexity, but it's key that the stinger can deliver venom consistently in a compact, self-contained unit. Dual motion also minimizes backflow.

These results were consistent with the authors' earlier flow visualization experiments. To confirm the initial findings, the team took microCT scans and used that data to create a scaled 3D-printed prototype to mimic the observed pumping behavior. This pumping motion was also filmed and analyzed frame by frame. The artificial pumping model showed the same pumping kinematics as biological stingers.

Future research may focus on more closely examining the material properties of the valves, as the team's synthetic polymer valve shows that very high elasticity is key to replicating the necessary deformations of the valve, along with low friction between the valves. Given the small size of the toxin pumping elements, it would be useful to investigate whether capillary action plays a role. Capillary action can help draw the venom into the venom canal, or alternatively, the venom may need to counteract capillary action to pull fluid out of the tissue.

Previous research has used the structure of bee stings as inspiration for the design of microneedles, tissue transfer devices, and drilling devices. The authors believe that their work will eventually find similar medical and microfluidic applications as artificial pumps.

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

Jennifer is a senior writer at Ars Technica with a particular focus on the intersection of science and culture, covering everything from physics and related interdisciplinary topics to her favorite movies and TV series. Jennifer with her husband, physicist Sean M. Carol and their two cats, Ariel and Caliban, live in Baltimore.