Bomber beetle hides a valve in its abdomen

The bomber beetle throws a hot and irritating defensive liquid when threatened. The phenomenon seems to be a simple giclée. But this jet consists of very fast pulsations, produced in the abdomen. To observe this hidden functioning, researchers used high-speed X-ray imaging.

The images made it possible to follow the relations between a tank and a reaction chamber. When the pressure increases, a flexible membrane deforms and helps to close a valve, interrupting the arrival of reagents. The expulsion of the liquid then lowers the pressure. The valve can reopen, allowing the cycle to resume and produce a new pulsation.

This succession is based on the mechanical properties of the device, without requiring a separate muscular control for each small jet. The researchers also suggest that breaks help limit warm-up. The animal does not have a manufactured weapon: it has an anatomy whose geometry transforms a chemical reaction into an intermittent defense.