Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Desert Millipede - Orthoporus ornatus

Desert Millipede - Orthoporus ornatus
Low desert just E. of Chiricahua Mountains, Cochise County, Arizona, USA
August 1, 2002
There were quite a lot of these big guys crawling around in the desert after a monsoonal rainstorm. They can reach 8 inches in length.

This is Orthoporus ornatus Girard, 1853 (Spirostreptida: Spirostreptidae), the common spirostreptid that occurs in southwestern deserts. It is known to mass aggregate, and there have been reports of "marching armies of millipedes" crossing roads near Big Bend Nat. Pk., Texas. Orthoporus is a very large, speciose genus that ranges from Oklahoma & Arizona, USA, southward to Argentina; it also occurs on Caribbean Islands. Scores of species are recognized, but only 4 are known to occur within the US.

We seem to remember reading somewhere
(have to try to track it down) that the longest North American millipedes were only about 12 cm and were in the Order Julida

Seeing Arizona millipedes - Orthoporus ornatus
How can you tell the males from the females.

The usual way that I use to normally sex Millipedes is the pair of legs missing in the 7th segment. I’m either very unlucky or these don’t sex the same.

I’ve also noticed some with black legs and some with Ted legs. Are they different species ?

I don't know.
Sorry Efi - I have no idea. Perhaps a millipede expert could weigh in.