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This Millipede and Beetle Have a Toxic Relationship | Deep Look

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 Biology   |   Environmental   |   Science
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This millipede uses deadly cyanide gas to keep predators at bay. But one beetle can tolerate the toxic defense and rides the millipede like a bucking bronco. Who will win this showdown in the forest?

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DEEP LOOK is a ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small.


Across Northern California, as the rainy season is ending and spring is taking hold, bees are buzzing, flowers are growing and hikers are hitting the trails.

But down at ground level, the pastoral scenery is concealing a surprising battle: relentless chemical warfare between bugs.

More than 200 species of millipedes emerge from their underground lairs every year during the winter and early spring months to forage for food and seek mates.

They have to fend off insects, mammals, reptiles and amphibians looking for a tasty meal. But they have a secret weapon – toxic chemicals they shoot from special glands. One Bay Area species, Xystocheir dissecta, carries deadly cyanide and benzaldehyde.

If they’re feeling threatened, these millipedes produce an invisible, odorless hydrogen cyanide gas that they spray at predators, and which is virtually toxic to all organisms. One byproduct is benzaldehyde, which gives off the scent of bitter almonds, as an additional signal that they’re secreting poison.

The millipedes don’t poison themselves, however. They’ve developed an immunity.

The cyanide can kill nearly any other animal trying to dine on the millipedes. Except one.

New research has found that one tough beetle is the only known predator in the world that can survive a direct blast of cyanide gas and keep going.

Brandt Weary, an entomologist, studied these hardy beetles last year for his senior thesis at the University of California Berkeley.

The beetles, known as Promecognathus crassus, love to eat millipedes, even though they are only one-fifth the millipedes’ size.

Weary wanted to know more about how the beetles withstood the millipedes’ tough chemical defense. He found that while many other beetles will avoid the cyanide-spraying millipedes, Promecognathus seeks them out.

--- How many legs do millipedes have?

Most millipedes have between 34-400 legs, and the record is 750!

--- Why do these millipedes “glow” or fluoresce?

One theory behind millipede fluorescence is that it's a warning sign. Moonlight has some UV light, so maybe an animal with better night vision can see the fluorescence even if we can't.

--- Which millipedes produce cyanide?

Only millipedes in the order Polydesmida produce cyanide. It's the largest order of millipedes with about 3500 species.

---+ Read the entire article on KQED Science:

---+ For more information:

Kip Will at UC Berkeley:
Science on the SPOT: Glowing Millipedes of Alcatraz:

---+ Shoutout!

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