Comment by Robert Mesibov: "Mating paradoxosomatids. The image captures the earliest stage, when the male approaches the female from behind and on top. Shame they weren't collected, we could have had an ID." ID to species requires detailed examination of the animals, especially the male. See the comments on the following sighting: http://canberra.naturemapr.org/Community/Sightings/Details/3377420
Unfortunately, you need to handle the animal to find out. A quote from Bob Mesibov: "How to tell if it's a mature male? http://www.polydesmida.info/polydesmida/plans.html With live Pogonosternum, you gently uncoil it and you should be able to spot the gonopods as yellow-gold structures about 1/3 of the way down the body from the head. The animal will resist uncoiling but if you hold it patiently it will relax and fully extend."