An interesting brief video. Insect wings (and other natural objects such as bird feathers and plant leaves) are superhydrophobic.
In analyzing the film, they found that when a drop hits the surface, it ripples and spreads. A nanoscale wax layer repels the water, while larger microscale bumps on the surface creates holes in the spreading raindrop.“Consider the micro-bumps as needles,” Jung said. If one dropped a balloon onto these needles, he said, “then this balloon would break into smaller pieces. So the same thing happens as the raindrop hits and spreads.”This shattering action reduces the amount of time the drop is in contact with the surface, which limits momentum and lowers the impact force on a delicate wing or leaf. It also reduces heat transfer from a cold drop. This is important because the muscles of an insect wing, for example, need to be warm enough to fly.
Reference: “How a Raindrop Gets Shattered on Biological Surfaces” by Seungho Kim, Zixuan Wu, Ehsan Esmaili, Jason J. Dombroskie and Sunghwan Jung, 8 June 2020, Proceedings of the National Academy of Sciences.
The high-speed film clip at the end of the video showing the swallowtail launching is absolutely beautiful. I'll just add that the butterfly depicted earlier in the video appears to be one of my all-time favorites - an Olympia Marble. Here's one I was able to photograph back in 2014: