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Photo#980833
millipede piggyback ride - Oxidus gracilis

millipede piggyback ride - Oxidus gracilis
Fabius, Onondaga County, New York, USA
August 16, 2014
Size: 17mm
I found these guys walking across the road like this. They stayed this way while I took them home in a jar in my bike bag and took this picture. The bottom one kept moving. The one on top was partially dislodged a few times, but he kept his grip and regained his position. Later they were separated and inactive.

Moved
Moved from Millipedes.

Possibly mate-guarding
Very interesting! This may be an example of mate-guarding, where the male (on top) sticks around after mating to prevent other males from mating with the female before she lays eggs. This has been studied in a tropical species, Nysodessmus python from Costa Rica, but I'm not sure if it's known how wide-spread the behavior is.

 
Cool!
I saw quite a number of examples of this behavior this summer.

Moved
Moved from ID Request.

Greenhouse Millipedes
Nice photo!
It appears to be a pair of Greenhouse Millipedes, Oxidus gracilis.
The one on top is the male, with the missing legs replaced by gonopods.
Interesting behavior, usually I find these under or around decaying wood, and facing each other when mating, not riding piggy back.
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