I'm no naturalist, but when I saw this picture, my first thought was, "Black and orange. I bet that little fellow's toxic and nasty." I looked up Apheloria, and sure enough, the little guy secretes cyanide.
Interesting how arthropods across taxonomic groups all settled on the same color code. I hope you didn't try to pick him up.
There is a large dark species(similiar to above but wider) of millipede(centipede?) I have picked up in the wet leaf litter of lushly forested foothills of the Blue Ridge in NC/SC that has a almost pleasant odor coming from their underside.
It reminds me and others who were with me of the "fragrance" of amaretto. I assume this is still cynanide, but not something (at least to me) that was immediately harmful. So far I have never had any adverse reaction when handling them, but obviously it is always a good idea to clean your hands after picking them up.
Thought I posted this comment yesterday (Brian, perhaps you can simply delete it if it is pending because of the href attribute I won't use here!)...
HP and Jules, the amount of HCN produced by these millipedes is just over 0.5 milligrams, enough to kill very small insects but only about 1/100th of the lethal dose for a human (and by the way, I often have several Apheloria virginiensis in the classroom, handled easily without an HCN discharge by kids)- the "bitter almonds" smell is characteristic of HCN (and interestingly, along the lines of asparagus urine, only detected by those with the necessary genetic trait)...
from what I understand, because HCN is a gas at room temperature and therefore storing would be problematic for the millipede, instead it mixes it "on site" by releasing the chemical mandelonitrile from storage chambers located on the sides of several segments into adjacent "reaction chambers" that contain the enzyme benzoyl cyanide; once these mix, they produce benzoic acid and HCN.
Just a note of query, also in the family Xystodesmidae, this may well be from the very similar and almost identical genus Sigmoria instead...
David, Thanks very much for the added information. Someone once told me the name of the species I have picked up before, but I can not remember or locate the reference now.
Thanks for the comments everyone. I have tried to figure out the species of this millipede, but I have not had any luck yet. It was fairly common, though. I must have seen more than 20 along the hike through the marshy area (lots of skunk cabbage) of a Westchester County, NY park. I didn't pick up any, although I do have fond memories of playing with the smaller millipedes I found under rocks in my backyard as a child (and recall their characteristic odor).
Very neat; millipedes are my favorite insect. In the trails near our home in Virginia, I've found numerous Spirobolid Millipedes, some of which have made it home to the terrarium (and some further to my fingers as I snap their picture, http://fertanish.net/speak/blogs/index.php/2009/12/16/millipede-un-wint… ). On rare occasion they seem to secrete a small amount of defensive fluid, but mostly they just poo on me.
Was it flat? I agree it looks like the Xystoesmid, although from the picture it looks like a Yellow Spotted Millipede...only about 3,000 miles from home.