This November, besides some epic tidepooling has been a waiting game for the rain to come. Ummm. . . still waiting! With rain comes slime molds, mushrooms, and GREENERY! So it was time to focus on whatever remaining insects were still hanging around. With only a few native flowering plants still hanging on, to the dirt and bark we go! Who lives under bark, and in the soil? Millipedes! Yippee!

Not everyone’s idea of cute, but millipedes deserve some mad respect! Below are photos of some species I’ve observed recently, all within Marin county CA and some general information about these leggy creatures.

But to start off, what’s the difference between centipedes and millipedes? It all comes down to the legs. Millipedes have TWO sets of legs per segment (4 legs per segment). Centipedes have ONE set of legs per segments (2 legs per segment). Legs, either two or four are connected to a single segment on the underside of the body. And while “centi” does translate from latin to 100, and “milli” 1,000, these critters don’t have those exact amount of legs. 

But there are more options, in case you can quite view those little leggies. 

• From the side:
  • Millipedes are more round, like a sausage
  • Centipedes have a flatter body 
• Threat Response:
  • Millipedes coil up, and can release stinky secretions
  • Centipedes bite! They can bite, mostly harmlessly, and they they run away. 
• Habitat:
  • Millipedes can be found in moist forested areas
  • Centipedes prefer dry environments 

Here are the most of the millipedes we’ve uncovered while exploring around Marin County. I’m still awaiting some identifications, so these ids are to the best of my abilities, and would love confirmation or any corrections!

Yellow-spotted Millipede:

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Gosodesmus claremontus:

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Interestingly, millipedes are not insects! Shocking, I know. They are in their own subphylum, which is different from Insects. 

• Kingdom Animalia, Animals
  • Phylum Arthropoda, Arthropods
    • Subphylum Hexapoda, Hexapods
      • Class Insecta, Insects

• Kingdom Animalia, Animals
  • Phylum Arthropoda, Arthropods
    • Subphylum Myriapoda, Myriapods
      • Class Diplopoda, Millipedes 

Genus Polyxenus, Bristle Millipedes: 

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Parajulid Millipede 

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Millis are of course well adapted to their life under bark, rocks, leaf litter and in the soil. Since it’s pretty dark down there only a cluster of simplified eyes known as ocelli are necessary. But when a predator comes along such as a ground beetle, amphibian or bird millipedes will secrete stinky fluid which can contain cyanide in some species, like the most common Yellow-spotted millipede. Yikes! Just another reason to wash wash wash your hands well after an excursion outside.  Which by now we should all know how to do, thanks Covid!

Millipede, needs ID

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Brachycybe producta:

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On iNat, when exploring for millipedes in Marin County, 18 species show up. The top five most observed species are: Yellow-spotted Millipede, Xystocheir dissecta,Brachycybe producta, Parajulid Millipedes, and Paeromopus angusticeps, and this is for all year long. When filtering for only observed in the month of November, it reflects pretty closely what I’ve observed. After those species, the amount of observations are five instances or lower. But like other odd or niche taxa, there are probably a lot of observations needing identifications which would change the rankings.

A 2002 checklist by R. Shelley found “11 orders, 24 families, 83 genera and 226 species” lives in California. But globally over 10,000 species are known. But like many other insects the actual number of species could be multiple times higher. Eeeee!

Nearctodesmus salix:

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Brachycybe picta

This millipede, Brachycybe picta was identified on iNat the morning I am posting it, and oooo la la it’s a first for iNat! Neat! According to iNatter herebespiders11, it is the “only species of Brachycybe in California with that bit of exoskeleton covering the head (“flabellate lobes on the pronotum”).

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Resources

• Centipede or Millipede? What’s the Difference? Carnegie Museum of Natural History
• Annotated CHecklist of the Millipeds of California (Arthropoda: Diplopoda) 
• Book: Pacific Northwest Insects by Merrill A. Peterson, 2018
• Taxonomy from iNaturalist
  • Class Insecta
  • Class Diplopoda