The prickly little beast on the right is a millipede in the genus Polyxenus. I found several of these living in the brood nest of a Temnothorax rugatulus ant, where they were probably scavenging on the ant's refuse. Huachuca Mountains, Arizona, USA
Temnothorax rugatulus, nest under a stone. Chiricahua Mountains, Arizona, USA
Urbana, Illinois, USA
