North American Millipede

Narceus americanus
Friday, July 23, 2010

This millipede can grow to be about twice as large as any other millipede that lives in North America. The record for these millipedes is 10 cm, and the largest millipede among these three is, by my best measurement, 10.2 cm.

These millipedes are cylindrical millipedes (distinguished from flat millipedes). As mentioned above, they can reach the great length of 10 cm, and are generally easy to recognize. They are black or dark reddish-brown with a red line on the edge on each segment. They, like all millipedes, have two pairs of legs on most segments, rather than one pair of legs on each segment (like a centipede.) However, also like all millipedes, the first four thoracic segments of a millipede have only a single pair of legs, whereas all of the following abdominal segments have two. The millipedes also have two short antennae.
Unlike centipedes, which are voracious predators, millipedes tend to eat decaying plant matter and the fungi it contains, and occasionally decaying animal matter. Millipedes are very important decomposers. Another species, the cyanide-producing millipede, demonstrates the importance of millipedes to the ecosystem.
“Since the [cyanide-producing] millipede crushes, filters and then recrushes its dead leaf diet, it increases the availability of nutrients 40,000-fold….The cyanide-producing millipede alone eats 33 to 50 percent of all the dead coniferous and deciduous leaves that come to rest on the forest floor. It is one of the most critical links in the entire soil foodweb.”
-- From the article Small in Size, but Great in Importance by Dr. Andrew Moldenke.
As a result of their food habits, millipedes are often found on decaying logs, on the forest floor, or in leaf litter. Despite their great number of legs, they are not fast crawlers. However, to avoid predation, many millipedes roll up into a ball and can secrete foul-smelling or even poisonous substances. Although not this species, some can secrete hydrogen cyanide, which is quite poisonous. Millipedes, again unlike centipedes, do not have poisonous fangs and do not bite. Their only defense is their secretions.
North American Millipedes live for several years, overwintering in rotting logs or in soil. In the spring, they emerge and mate. The females form carefully constructed nests out of regurgitated food, and afterwards lay their single egg into it. They will brood the egg by wrapping themselves around it. In several weeks it will hatch as a nymph, or “incomplete millipede.” Newly hatched millipedes generally have only three pairs of legs, but add more with each molt as they grow. Millipedes usually take 1-2 years to reach adulthood, and some species can be surprisingly long-lived, up to 11 years.
These three millipedes were captured on the side Route 613, crawling on the forest floor.   
Article by Hazel Galloway
See images of this organism here, courtesy of