After seeing this example, I thought I’d start a thread for people to share examples or info about UV fluorescence in Nature. I don’t think there’s been a general thread for this before, but please let me know if there’s an old one I didn’t find via search.
I’ll start it off with one of my favorite observations, which is of this (likely gravid) solifugid, which Damon Tighe shone his blacklight on. You could see inside the animal, and those are probably its internal organs being pressed against the exoskeleton by its eggs.
I don’t know much about UV fluorescence but I recall a biology professor who worked on scorpions tell me many years ago that some organisms alleged to fluoresce under UV really only reflect. Seemed like an interesting distinction. Anyone have insights about that?
fluorescence generally means you’re absorbing one wavelength and emitting another. most UV flashlights emit light that is mostly invisible to humans, except for maybe a little that folks would describe as purple or pale blue.
so if you shine a UV light on something and see other colors emerge, you’ve almost certainly got fluorescence. but if you see the same purple or pale blue that your flashlight emits, then it’s possible that’s just reflection.
here’s a spider observation of mine: https://www.inaturalist.org/observations/164137128. if you look at the spider, it’s showing up as the same pale blue that my flashlight emits. so it’s possible that it’s just reflecting the pale blue light in that case. (there might also be some faint fluorescence, but i’m not sure.) but the lint in its web is glowing intensely and with different colors. so that’s definitely fluorescence. if you look at the first part of the associated video, the spider has caught something that is oozing a bit of bright green, and whatever that is is definitely fluorescent, since there’s no green in the light beam.
Wow, fluorescent rats are a new one for me. Was this a wild rat? Some lab animals are modified to have fluorescent proteins (e.g. do a google search for fluorescent green rabbits and you’ll find some relevant articles). There are some other neat examples of fluorescence in more complex animals, though (compared to the solifugid). I like to share this example of fluorescence in sea turtles.
Nothing too out of the ordinary, but here’s a shot of a bark scorpion. I had some decent photos of greenhouse millipedes under UV, but can’t find them and apparently didn’t upload them to iNat. :-/
UV fluorescence intrigues me. Maybe 12-14 years ago I put together an after school science program for kids on UV lights. SO MUCH STUFF!
Some random snippets from memory.
There are different wavelengths of UV light and different substances do not react to all UV wavelengths light. Shorter wavelengths are not safe for human eyes or skin.
Many flowers have UV markings to help guide insects to their pollen.
Chlorophyll is UV reactive, fun experiment*
Snake skin is UV reactive
Human fingernails and teeth are UV reactive. EDIT: huh! I just noticed my white hairs (which grew in during the pandemic) fluoresce under a black light
Many nuts are UV reactive
Many minerals that look dull in sunlight have magnificent colors under different UV wavelengths.
Urine marks are fluorescent under UV light. I use the feature to police the carpet for pet accidents
Pest control professionals will look for mice/rat urine trails to determine where to place traps.
Fun nature experiment for kids
Chop up plants, extract the chlorophyll and see the green chlorophyll appear blood red under a black light.*
(From memory, so make allowances)
You need :
Green leaves to mush up (spinach is an easy cheat)
UV lights (prefer the longer wavelengths for safety)
Blender or chopping/muddling tools
Isopropyl alcohol
Coffee filter and holder
Clear glass beaker, large test tube (or similar)
A dark space to view the extract with a black light.
Process
Have kids collect soft green leaves (or use a bag of spinach)
Let them chop/mash the leaves into pulp (or use a blender)
Put leaf mash into a coffee filter on a filter holder
Set the coffee filter holder over the glass
Pour a couple ounces of isopropyl alcohol into the filter
Let it drip and gently squeeze a little more juice out of the filter
The beaker will have a green fluid of extracted chlorophyl. Take the beaker into the dark room and shine a UV light on it. The green liquid instantly appears as blood red! WHOOOOO!
Last summer I was in western Utah with a group of botanists and we went looking for scorpions one night. We found this one, about 3 inches long. While we were looking at it, moths were attracted to the light so one person grabbed a moth and held it out for the scorpion, which took it and walked around, waving the moth in its pincer before taking its prize down a hole to much on it.
It turns out that people are finding more and more mammals that fluoresce under UV light. Wombats, rats, flying squirrels, and spring hares have been found to fluoresce under UV light. I suspect there are probably more and that people just haven’t been looking.
yes. i was really surprised when i saw the greenish-blue blobs moving around while shining my UV light at night in the park. up until just a few years ago, there were very few mammals that had been recorded in the scientific literature as exhibiting UV fluorescence, and the ones that did were known to fluoresce pink (in my area, opossums and flying squirrels). so i wasn’t aware that rats would also fluoresce, too, let alone fluoresce greenish-blue.
it’s only been in the last maybe 3 years that articles have appeared noting the UV fluorescence of the rats that are so common in human landscapes around the world (Rattus rattus and Rattus norvegicus). and i think that either kicked off or was an early part of the recent wave of researchers looking for (and finding) fluorescence in all sorts of mammals.
why not just shine a light on an actual leaf on a live plant? not all leaves exhibit the same level of fluorescence, but there are some that fluoresce a really deep crimson. and the notable thing about fluorescence in chlorophyll is that it sort of has a memory. once a part of a leaf has been exposed to UV light, it takes a while for that part of the leaf to recharge before it will fluoresce at the same strength again. so you can put an object with an irregular shape on a leaf, shine a UV light on it, remove the object, and then shine the light again, and you should see the shape of the object in the leaf – sort of like a solar print. you can tie this into a lesson on how photosynthesis and how chlorophyll works.
and it might even be interesting to shine a UV light on a known sample of leaves from plants that exhibit different levels of fluorescence. then have the students hypothesize why there are differences, and then test their hypotheses by having each of the students (or teams) predict a plant that should fluoresce a lot and one that should fluoresce just a little, and then put all of the plants under UV to see whose predictions are the best.
I guess you would need to know which species would fluoresce with a little razzle dazzle. Do you happen to recall one with a notable reaction?
Also, I set this up because kids love doing experiments. so, you can teach other science-y things like lab safety, equipment, and processes. The leaf experiment was just one of several activities developed for this after school science program, but it was one of the most popular ones.
I tried that just now with a sampling of plants from the refrigerator and the yard. None of them fluoresced very brightly as the extracted chlorophyll did with my UV light. The one that reacted the most was a green onion and a fresh bay leaf, but they were just a muddy orange or reddish brown.
I wish I’d known that for my program. If I ever find a leaf that fluoresces well, I am definitely going to try that just for my own satisfaction!
We frequently have northern flying squirrels in our bird feeder and I tried the blacklight trick just last week. Their dorsal sides look dark reddish-brown but their bellies glow bright pink. I’d like to try to get photos but I’ve also read (but can’t remember where) that the UV light might harm their eyes just as it would for us. Can anyone confirm this? Also, I’d love to hear your tips if you’ve captured them on camera while using a blacklight.
Since flying squirrels live on tall trees, it’s very hard to get a good UVIVF picture, unless you set up a bird feeder right next to your window or spent thousands of dollars on modified speedlite (Godox AD200 speedlite + UV/IR block filters).
Here are some pictures of UVIVF flying squirrels: https://leerentz.wordpress.com/2022/02/15/glowing-pink-flying-squirrels-biofluorescence-revealed/
To capture an UVIVF picture of flying squirrel at night, you probably need a very powerful UV light, example (Blak-ray UVP B-100A), I knew some people use Blak-ray B-100 for mineral hunting.
I have a Blak-ray B-100, it’s heavy but it’s a great UV light.
Thank you for the links. Our flying squirrels come to a feeder that’s about 5 feet off the ground. They’re very unafraid and I can get within a few feet. I regularly get photos of them on my trail cam mounted on a nearby tree. I got a cheap blacklight from a sporting goods store so I’m not sure how strong it is (it doesn’t seem to be very strong). But thank you for the warning – I certainly don’t want to harm them and have used the light very sparingly. But since there’s an iNat page devoted to UV fluorescent taxa, how else would I prove that what I see does indeed fluoresce?
here’s a video that sort of shows that happening: https://youtu.be/aJh5bosgFQQ?t=187. i think the phenomenon is called the Kautsky effect. it would be interesting to ask students to develop hypotheses for why it happens.
Most of cheap UV flashlights do not emit enough UVA, just blue+purple light.
You could try to set up an UV flood light on top of your bird feeder, pointing the UV light downward. Please do not point your UV flashlight directly at the flying squirrels’ face.
UVIVF photography is not easy, you need to shoot in completely darkness. That’s why most of UVIVF flying squirrels pictures are dead flying squirrels, such as this one: https://www.smithsonianmag.com/smart-news/flying-squirrels-glow-fluorescent-pink-under-ultraviolet-light-180971397/
A short (10mn) video by Derek Muller (“Veritasium”) on 
I wish I’d known that for my program. If I ever find a leaf that fluoresces well, I am definitely going to try that just for my own satisfaction!