This sent me down a rabbit hole of research this morning.
Hummingbird moths are adorable. They really do behave like hummingbirds, hovering to drink nectar or, in this case, delicious orange juice. Hummingbird moths are actually far more placid than hummingbirds, so you can often get quite close to them like this and they seem to not care at all.
But one thing I wanted to explain before reblogging this: the wingbeats in this video. They look super slow, somewhere between 5-6 beats per second. That doesn't sound slow, but even the largest and slowest hummingbird known beats its wings twelve times a second.
Obviously, this is an optical effect of the camera and video encoding used here. The day is bright enough that the camera is able to capture unblurred images, but it still has both a maximum shutter speed and a rolling shutter: this can create some really funky distortions depending on the speed of the object you're trying to capture.
So, what you're actually seeing is little slices of the moth's wingbeats, which happen to be slightly out of sync with when the camera is capturing images: if you look closely, you can see moments when it looks like one wing is flapping up while the other is flapping down, for example. That's one of those artifacts of the rolling shutter.
But this led me to wonder what the wing speed of a hummingbird moth is. This turned out to be harder to determine than one would think. There's no videos of hummingbird moths on youtube that were taken with anything other than a standard digital camera, and obviously the shutter speed isn't fast enough. So, I went on a literature dive.
Wikipedia is usually the place to start a search for primary sources on a topic you're not familiar with, but Wikipedia doesn't list anything for the hummingbird moth species I looked at. General educational websites don't tend to cite their sources: some of them say 40-80 beats per second, but where'd they get that number from? Perhaps someone simply intuited that they flap their wings around as fast as hummingbirds, or perhaps someone misread "hummingbird" as "hummingbird moth" one day, you honestly don't know.
What you want in this case is a grade-A nerd that went out with some fiddly equipment and did some math, then documents it to a ridiculous degree.
Searching Google Scholar required my feeble New Year's Day-brain to remember "hertz" is the preferred unit for fast objects: it's literally the same as "beats per second", it's just more general and can be used for any fast, repetitive event. As a result, I've found out that scientists are apparently very interested in hitting hummingbird moths with tiny projectiles or forcing them to take hard turns, partly because a lot of people want to make really small drones these days, and self-righting flight is important for something that weighs less than a french fry.
These sources list average wing flaps as 15 - 28.8 Hz, but these were under adverse conditions, namely, y'know, getting pelted with little projectiles and being forced to do Deja Vu-worthy skid turns. So I kept looking, and adjusting my search terms.
Eventually, I found the answer, for at least one species: Photographed in an animal wind tunnel with a high-speed camera, the hummingbird hawk-moth (Macroglossum stellatarum) was found to have an average wing speed of 69 Hz.