ive seen p.wahlbergii have a defensive display, they flatten out and elongate their abdoment, exposing the "eye" spot fully, and the abdomen is kind of...i dunno, pulsating? throbbing... a bit like a bee sting. and the forearms are opened out almost fully, and to the sides, as if to say "look how massive i am". and the forearms are kind of moved around a bit, its hard to describe the exact motion, but its quite distinctive, if youve seen it youll know. ive seen them do it to each other (and also once or twice to food which was bumping into them or was too big for them to have a go at, or if they just werent feeling up to it). although that was only with small nymphs (L2-L4 or so). so yeh. thats one example i know of.