I never really thought about this, but in considering the kinetic impact of a large raindrop on a small or delicate insect I would think it could be devastating. Are they knocked to the ground? Injured? Unharmed?
No answers really, but just wanted to say this is a great question. I’ve wondered it myself. Even if the impact didn’t injure the critter (which I suspect it might not, because bugs and things are quite robust in some ways) they’d be messed up with the surface tension of the water and I can’t imagine anything happening but a quick interface with the ground (even a drop of water on an ant when I’m having a shower renders the thing helpless in this way - and it’s already on the ground).
I guess instinct must take over - you don’t tend to see any flying things much, even in light rain. I suspect they head for cover pretty sharpish.
Here is what the straight dope has to say about it.
I’ve seen butterflies get hit and they did fine. Flies did ok too. Only during a deluge are they in trouble.
Ever seen a housefly fly headfirst into a bathroom mirror, bounce off, and repeat the same procedure over and over again 20 times in a row? I think that if a fly can ignore that sort of intentional abuse, a little raindrop isn’t going to phase it much.
Remember, muscle/bone/exoskeleton strength generally goes up by diameter squared, whereas mass/volume (and thus kinetic energy and weight) goes up by diameter cubed, so handling objects many times your diameter size (as well as flying yourself straight into a mirror) is a lot easier when you are insect-scale.
The answer to your question is as elusive as the butterfly itself.
Here is a piece from Scientific American written by Michael Raupp, professor of entomology at the University of Maryland. He opines as follows:
This entertaining analogy suggests to me that a butterfly caught in a deluge is toast. However, a team of French physicists reporting on the hydrodynamics of droplet impact on various surfaces offers this view:
This doesn’t really get us very far since I have no way of verifying Professor Raupp’s bowling ball conclusion. He also fails to discuss specifically the impact of a raindrop on the butterfly’s wings, while the physicists don’t refer to the impact of a raindrop on the butterfly’s body.
It’s a good question.
The critter might be better off flying than sitting on something. I say this because I once tried (please forgive me) killing houseflies by shooting them point blank with a CO2 pistol, using just the blast (no pellet). If there was nothing on the other side of the fly, it was usually just displaced rapidly by a few inches and flew off. If I angled the gun so the fly was propelled into something (like a window frame), the fly usually did not survive.
Those critters are pretty tough.
I think a butterfly wouldn’t fare as well flying in a hard rain as a fly or bee would, simply because the butterfly’s wings aren’t as compact.
Many times, when watering the garden, I’ve directed the hose toward a flying insect. This is much more serious than a single drop of water, yet it merely slows them down for a few seconds, then they’re on their merry way. Of course if I hit them with the full force of the jet of water, it’d probably do serious damage.
According to “Bee Movie”, bees can’t fly in the rain.
Does that count as a cite?
This is a good chaos theory question.