Why do water-meter bedbugs not sink? - briefly
They stay buoyant because their exoskeleton traps a thin air layer and is hydrophobic, making their overall density lower than water. Surface tension further supports the insect, preventing it from submerging.
Why do water-meter bedbugs not sink? - in detail
Bedbugs placed on a water‑meter surface remain on top because their bodies are lighter than water and their exoskeletons repel moisture. The cuticle contains a waxy layer that prevents water from wetting the surface, creating a barrier that traps a thin layer of air around the legs and abdomen. This trapped air increases buoyancy and reduces the effective density of the insect, keeping it above the liquid level.
Two physical mechanisms dominate the effect:
- Surface tension – the insect’s legs are thin enough to be supported by the liquid’s surface film. The cohesion of water molecules at the interface generates a force that counteracts the insect’s weight.
- Hydrophobic cuticle – the waxy coating repels water, maintaining a dry air layer that further lowers the overall density of the organism.
Because the water‑meter environment is typically composed of smooth, non‑porous material, the insects cannot penetrate the surface to reach the underlying water. Their small mass, combined with the above properties, ensures they stay afloat rather than sink.