www.ukbutterflies.co.uk

https://www.bbc.co.uk/news/science-environment-55719955 which includes a link to the paper

I thought that the flexible wings of a butterfly was seen more clearly in, even slower motion during takeoff and at more than 240 frames per second (someone's iPhone).
Another comment I would like to add, was that a butterfly starting with wings closed had a slight advantage from predator, in that, it was quite a long way from flower after second downward beat, making full use of the first downward beat:

"The fastest Cabbage White in the West"

https://youtu.be/StfnYdl1A_4

1/10th real time (Slow motion at 1/5, slowed down by 50%), approximately 240 frames/sec. (iPhone), Piers Brassicae, might have escaped from near someone's cabbage patch.

August 25th 2017
"It was thought Pieris Brassicae was seen mating in flight, more than most other United Kingdom resident species of butterfly.
On this occasion, the male appeared to be taking the lead, it’s wings outside of the female, possibly offering her more protection and took off first.
I did not put them in a wind tunnel":

https://youtu.be/oeKmTxlEdtM

Interesting article, Jon. Many thanks for posting.

After takeoff, some more interesting observations, that might of helped a design of "slow motion", underwater robots.
One might remember in the 1970s seeing a "Cabbage White" in August, "climb" a house, go over, somewhere near the chimney pot, then descend very rapidly on the other side. If one looked at the rapid decent in slow motion (the males often do it, looking for females), they hold their wings closer together, up to about, a 90º angle between the wings, to descend fast and keep a required stability.

Kind regards.