Confidence: I'm as sure as I can be.
Notes: At first these male Gold Swifts appeared to be dead and parasitised- I hadnt seen this behaviour before. I had observed several 'lekking' just before hand just after 9pm on a warm evening. They turned out to be alive and well and seemingly releasing scent from the structures on their undeside. UK moths says they are supposed to smell of pineapple but I didnt notice it this time. Last pic shows one sitting normally after being disturbed.