It is a particular set of spines on the tibiae of the forelegs.

The website's statement of orange tinge to the underside of the abdomen is in error ( should be thorax).
http://www.aus-lep.com/ThumListFam/S...es%20hylas.htm
http://www.aus-lep.com/ThumListFam/S...es%20picus.htm

In pix 1 the foreleg is orangey.
In pix 2 the thorax is orangey, but the legs appeared overexposed.
In pix 3 it is obvious.

I would say all three are Cephonodes picus.

TL Seow