Excerpts from Jim Conrad's
from the December 2, 2001 Newsletter issued from the woods just south of Natchez, Mississippi, USA
Wednesday morning after one of our first downpours I noticed that some small millipedes ("thousand-leggers") had drowned in the water standing next to my outside kitchen. I needed a millipede picture for my nature-study site so I gathered up a specimen and you can see the resulting scanned image below:
About 600 millipede species are found in North America north of Mexico and they are often hard to distinguish. However, this was a pretty distinct-looking species and I chanced upon a good illustration of the drowning victim, so I am pretty sure that it is PACHYDESMUS CRASSICUTIS. Apparently it has no English name, and it is found only in Louisiana and southern Mississippi. This species has no eyes and, like all millipedes, feeds on various plant materials, especially soft, decomposing plant tissues. They are perfectly harmless to humans.
An interesting scientific paper about this species was found on the Internet. Apparently a researcher noticed that when fire ants attack this millipede the fireants are the losers. This so rarely happens in nature (fireants generally overwhelm all their enemies) that the researcher wondered what the millipede's weapon was.
Chemical defenses were suspected, so small squares of filter paper were touched to living Pachydesmus crassicutises, then gas chromatography and infra red photospectroscopy were used to examine any chemicals found there. It was discovered that this millipede defends itself with benzaldehyde and hydrogen cyanide. In other words, it sprays its attackers with cyanide, and cyanide is one of the most deadly chemicals known to science.
You can read an abstract of this paper yourself at http://www.navi.net/~rsc/nitrilo1.htm. That's a big page so use your SEARCH tool to find the words "Science, 138:513, 1962," which also happens to be the literature citation.