The Frog-legged Beetle.
Sagra is a genus of beetles belonging to the family Chrysomelidae, commonly referred to as frog-legged beetles or kangaroo beetles. They are around at the moment, and this picture was taken in SaiKung.
IN this photo I was intrigued to see a host of small black-headed ants that are taking the sap from the stem/plant where these beetles had been chewing and eating previously.
About this pair....I am not sure if they are about to mate or if this is another male seeing off a rival. I have read that some males will try to assert their dominance by mounting his opponent, in a non-sexual way. The losing male will wait for the winner to finish mounting him, and then retreat when released. The beetle below is missing part of its hind-leg which could have been after fighting.
These beetles often "perch" with their legs extended which has been suggested is a threat posture, and I noticed this in many of the beetles that I have observed over the last week. I have not witnessed the behaviour recorded by others that the modified legs can play an important role in males fighting over a females. A paper from 1993 described what is basically beetle leg wrestling where a male will initiate a “one side attack”, or both males will start an intense fencing match, trying to subdue and ward off their opponent.