Life Science Noteworthy SERIES: Invertebrate of the Week

Invertebrate of the Week #20 – Motyxia Millipedes (Motyxia sequoia)

Meet the conspicuous glowing millipedes of Sequoia National Park; the brightest of all the Motyxia species. They glow, they make hydrogen cyanide, they star as the main antagonist in the fourth level of an iPad game. What’s not to love?

Motyxia millipedes are small creatures, reaching only about 4-5 cm in length and 4-8 mm wide. These exclusively nocturnal millipedes spend their days nestled beneath the soil in live oak and giant sequoia forests. When the sun sets, a currently unknown environmental cue causes them the to emerge from their burrows and cruise about in search of the decaying vegetation they feed on.

Motyxia sequoiae millipede displaying bioluminescence while walking in the dark.
Motyxia sequoiae bioluminescence. Image: National Geographic.

Nothing unusual so far, but what is unusual is the fact that while other nocturnal creatures may be doing their best to remain hidden, Motyxia millipedes confidently stand out. The millipedes emit a bright, steady glow; seemingly without a care in the world as to what might be watching them.

The millipedes are blind, so this illumination is not a visual cue intended for conspecific communication. Rather, it is believed to serve as a warning sign (i.e. aposematism) to potential predators, similar to how animals like monarch butterflies use bright colors to communicate to predators like birds that they are toxic.

Why would predators want to avoid Motyxia millipedes? It turns out that these millipedes pack a poisonous punch. If you get close to one, you might notice an almond-like odor emitting from their body. That’s a clue to the type of toxin employed by these conspicuous little Polydesmidans. Can you guess what it is? Hydrogen cyanide.

Though the amount of hydrogen cyanide produced by these millipedes isn’t enough to kill a human or other potential mammalian predators, it’s almost certainly sufficient to create a bad enough experience to deter future encounters.

So next time you find yourself among the Sequoias, keep an eye out for these conspicuous little millipedes. Just follow the light and the smell of almonds.

References and Further Reading