Saturday, October 10, 2015

Millipede at Ritter Springs

Kids find the darndest things
    -With apologies to Art Linkletter

On a Discover Nature field trip with Watkins Elementary students last week, we had the kids roll over a few decaying logs which reliably yields interesting critters.  In this case they turned up this millipede.

Round-backed millipede
Most kids will automatically think it is a centipede, as they get a lot better publicity than the sluggish millipede.  Centipedes move fast, millipedes much slower.  Centipedes have one pair of legs per segment while millipedes have two pair, a difficult distinction to make when they are in motion.  It is much easier if you can flip them on their back.  You can only do this with flat-backed millipede species as the round-backed species will roll up into a tight defensive ball.

Two pair of legs per segment = millipede
Millipedes can be difficult to identify.  For one thing, except for the head and tail the intervening segments are all the same, no distinctive shape or unique wings to rely upon.  Color and general appearance can be deceiving.  As an example, look at these two totally different genus and species below which are frequently confused.

Euryurus leachii - Steve Dunbar
Jon Rapp

I had previously found this same millipede.  After reviewing many pictures on, I finally called it millipede - genus Sigmoria or Autorusus.  I sent photographs to Bugguide which is followed by lots of professional and citizen scientists who are knowledgeable and passionate about their niche in the insect world.  In this case, within 24 hours we had an ID of Auturus evides, confirmation that it was known to occur in Missouri, and even photographs by our friend Jon Rapp from Columbia, Missouri.

There is no information online specific to the Auturus genus.  They are members of the Euryuridae family which has 11 species in 2 genera.  Rowland Shelly* is a frequently quoted expert in the field.
"They are one of the few millipedes with a precise habitat; I always find euryurids in association with decaying hardwood/deciduous logs or stumps (rarely pine) near water sources like streams, creeks, seepages. If no water nearby, then no euryurids." *
Millipedes get little respect on the web.  Even the order Polydesmida or flat-backed millipedes like ours above only gets three small paragraphs in Wikipedia.  Fortunately they don't seem to take it personally.  This is the order that contains all the cyanide producing millipedes.  I don't know if our A. evides excretes cyanide but I wouldn't want to do a taste test and I take the precaution of telling the observers to never lick a millipede.

Millipedes are scavenger herbivores and lack the biting mouth parts that  predatory centipedes have, meaning that they can be handled safely.  They consume dead and decaying wood and leaves.  Some have bright aposematic colors advertising their toxicity (or in the case of mimics, pretending they are toxic to scare off predators).  Either way, I suggest that you never eat a millipede.

Update 3-29-2017
The BugLady's column "Bug of the Week" was filled with fascinating millipede details, the highlight of which is the lemurs that lick millipedes as an insecticide and a high!

* Rowland Shelly is Curator of Terrestrial Invertebrates at the North Carolina State Museum of Natural Sciences, Raleigh.
Information on millipedes in general is on this Wikipedia link.

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