Wildlife Wednesday - butterfly tree

In Exmouth, we took a stroll to the beach that took us through some scrub. There was this scraggly looking tree that seemed to shimmer. I took a photo (but of course it doesn't look as shimmery as it appeared, so you'll have to believe me how shimmery it was :) ) and when we drew closer it was hundreds of butterflies all on the tree.

I've never seen anything like it and I don't know what type of butterflies they are, but it was magnificent.

And although I've looked in my books and online, I still can't find out what they are.