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> Rain drops are heavy and can be damaging to delicate surfaces like butterfly wings, which have protections=:
> 
> https://phys.org/news/2020-06-armor-butterfly-wings-heavy.html
> 
> "An analysis of high-speed raindrops hitting biological surfaces such as feathers, plant leaves and insect wings reveals how these highly water-repelling veneers reduce the water's impact. 
> 
> "Micro-bumps and a nanoscale wax layer on fragile butterfly wings shatter and spread raindrops to minimize damage.
> 
> ***
> 
> "The research showed how microscale bumps, combined with a nanoscale layer of wax, shatter and spread these drops to protect fragile surfaces from physical damage and hypothermia risk.
> 
> ***
> 
> "Raindrops pose risks, Jung said, because their impact could damage fragile butterfly wings, for example.
> 
> "'[Getting hit with] raindrops is the most dangerous event for this kind of small animal," he said, noting the relative weight of a raindrop hitting a butterfly wing would be analogous to a bowling ball falling from the sky on a human.
> 
> ***
> 
> "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.
> 
> "If they have a longer time in contact with the cold raindrop, they're going to lose a lot of heat and they cannot fly very easily," Jung said, making them vulnerable to predators, for example.
> 
> Repelling water as quickly as possible also is important because water is very heavy, making flight in insects and birds difficult and weighing down plant leaves.
> 
> Comment: The original design of butterfly wings had to include this protection mechanism or butterflies would not have survived. Not by chance