This is Adela reaumurella. Google suggests a couple of common names have been attached to it — Green Longhorn and Metallic Longhorn — but neither seems to have much traction. And actually, the fact that so many British moths have established English names is the exception rather than the rule; if you’re interested in insects, you’re going to have to tangle with Latin sooner or later.
Anyway, this is a species I saw in the local woods a couple of years ago. They’re pretty tiny, the wingspan is less than 2cm, and it would be easy to walk past without noticing them; but they are tiny peacocks. Only the males have those ludicrous antennae, and they are a direct equivalent of a peacock’s tail.
But it wasn’t the antennae that made me notice them; it was the dancing. There were perhaps a dozen in the group I saw, perched in a patch of sunlight, and they kept flying up couple of feet and then drifting back down to their leaf; and all the time they were in the air they held their antennae up above their heads in a V shape.
There’s a rather wobbly video of a much larger swarm here.
If they were birds, I would say they were lekking. A lek is where a group of males — grouse, birds of paradise, or whatever — gather in one place to perform next to each other, compete for the best display spots, and try to win the attention of females.
Seeing a longhorn moths doesn’t quite scratch my itch to go to New Guinea and see birds of paradise; but it’s still a fun thing to find.
» ‘Longhorn moth, Adela reaumurella’ is © nutmeg66 and used under a CC by-nc-nd licence. ‘longhorns’ is © Nigel Jones and used under a by-nc-nd licence. ‘Adela reaumurella-07’ is © IJmuiden and used under a by-sa licence.