# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/Dde4UrFSH7I
- **Gondola URL:** https://gondola.cc/posts/70577829-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/663a3cb807.jpg
- **Posted:** 2026-09-19T20:35:09.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

The bombardier beetle stores a binary chemical weapon in its abdomen and detonates it roughly five hundred times per second without cooking itself.

Each of the paired pygidial glands is split into two compartments. The outer reservoir, wrapped in muscle, holds an aqueous mixture of hydroquinones and hydrogen peroxide. The inner reaction chamber is thick walled, reinforced, and lined with catalases and peroxidases. Separated, the fuel is inert. Opened, the chemistry turns violent in under a millisecond.

- Catalase decomposes hydrogen peroxide into water and oxygen, releasing roughly 98 kJ per mole
- Peroxidase drives the oxidation of hydroquinone into p-benzoquinone, a potent irritant
- The combined enthalpy carries the charge to about 100 degrees Celsius and flashes part of the water to steam
- Steam pressure expels the spray at an average of 11.6 metres per second through a turret the beetle aims over most of a sphere

Hermann Schildknecht at Heidelberg identified the reagents in the late 1950s. Thomas Eisner spent four decades at Cornell on the delivery system, and in 1990 he published with Jeffrey Dean, Daniel Aneshansley and MIT strobe pioneer Harold Edgerton, showing the discharge is not a stream at all. It is pulsed, between 368 and 735 times per second, mean 531 Hz, with a typical discharge lasting about 12 milliseconds.

The cause stayed unknown until 2015, when Eric Arndt, Wendy Moore and Christine Ortiz filmed live beetles in the synchrotron beamline at Argonne National Laboratory at 2,000 frames per second. No neural clock is involved. Each explosion raises chamber pressure, a flexible membrane inflates and shuts the inlet valve, the charge vents, pressure collapses, the membrane relaxes and the next slug floods in. The oscillation is passive, and the pauses between pulses are what keep the chamber walls below failure temperature.

Evolution built a working pulse jet and put it on six legs.

#stemantics #biomimicry #entomology #chemistry #engineering

## Stats

- **Views:** 58,228
- **Likes:** 924
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- **Comments:** 17

## Tags

engineering, chemistry, entomology, stemantics, biomimicry

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