It seems a special guest joined U2 on stage during the Brisbane show a couple of weeks ago...
From Willie Williams' tour diary:
"The gig itself went well enough, with a couple of funny moments. When the lights came up at the top of the first number, ‘City of Blinding Lights’, I could see in the camera close up that The Edge had a large green praying mantis sitting on top of his head. He really did – I’m not making this up. There was a bright green mantis happily cleaning its mandibles perched on Edge’s black beanie. It wasn’t overly noticeable on the stage screens (and besides there’s a hell of a lot going on at that point in the show) but at mission control on the TV monitor for Edge’s camera we could clearly see the little chap perched there, in the best seat in the house. It sat there for a minute or so, then started to move about, exploring his new black woolly domain. It crawled forward and had a look down at Edge’s guitar technique, then turned around and wandered back over the crown of Edge’s head until we realised that a few more insect steps and the thing might fall down the back of Edge’s neck, which would have been highly entertaining but possibly disastrous for the show. Mercifully it held on until the blackout before Vertigo, when The Edge’s guitar tech discreetly slipped on stage and flicked it into oblivion."
It could only happen to The Edge XD