UV Florescence

 iNat has a great project dedicated to UV florescence.  

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.

From left to right: visible light, UVIVF, and UV reflected light.  From: https://www.wildflower.org/magazine/native-plants/a-different-light

This article with beautiful UV and visible light photos helped me understand the difference between UV reflective and UV-induced fluorescence (UVIVF) images. However, I think many people, including the author of that article, are still confused about the biological meaning of UVIVF. For example, the False Gromwell writeup implies that insects can see UVIVF to help find flowers that are otherwise inconspicuous.

But UVIVF is never normally visible…except maybe as an added glow. The best example is laundry detergent that makes whites brighter. By adding a UVIVF chemical to the detergent, clothes actually slightly glow in any UV light, making them appear brighter.  

Meme by apermar.  Veritaseum explains more on Youtube.

Photographs of UVIVF in darkness show the extra brightness we see in sunlight, but usually don’t notice.  However, UVIVF may be biologically important to some animals, such as scorpions, frogs, and flying squirrels.  Taboada et al. (2017) documented biofluorescence in response to UV light can contribute between 18 and 29% of the total light emitted from some species of tree frogs under natural, dimly lit conditions.  

Flying squirrels fluorescence is hypothesized to aid in camouflage against a backdrop of lichens emitting similar fluorescent spectra, or potentially in Batesian mimicry of co-occurring predatory owls with similar biofluorescent profiles.

Biofluorescence could be a useful tool to document amphibians where the small, cryptically colored, and/or nocturnally active species can be hard to locate among leaf litter or dense vegetation. 

The study of UV florescence is relatively new, with new discoveries being made every year.  For example, 2017 was the first documentation (published paper) of an amphibian with natural fluorescence. A 2020 paper then found fluorescence widespread among amphibians.  iNat users had documented fluorescent amphibian from frogs starting in 2018 and salamanders in 2021.

A photo I took with a 390-405 nm (just barely UV) blacklight.  Most UV photographers use a 365nm (UV-A) flashlight, sometimes with extra filters to block all of the blue and violet light. 

More discussion of florescence can be found on the iNat forum.  

Taboada, Carlos; Brunetti, Andrés E.; Pedron, Federico N.; Neto, Fausto Carnevale; Estrin, Darío A.; Bari, Sara E.; Chemes, Lucía B.; Lopes, Norberto Peporine; Lagorio, María G.; Faivovich, Julián (2017-03-13). "Naturally occurring fluorescence in frogs". Proceedings of the National Academy of Sciences. 114 (14)

Lamb, J.Y.; M.P. Davis (2020). "Salamanders and other amphibians are aglow with biofluorescence". Scientific Reports. 10 (1): 2821.

Solar Insolation in the West

Light on the Dunes

Lime Night Life Light

Ah, back to the hammock

cold paws, correct breathing

shoulders relaxed
writing in bed, flowers
scattered around
my dark shape
amid
innumerable dark shapes
under an empty sky
full of fluttering
moths
whose white noise fills up the valley
called to my reading
my lime night life light
a babbling brook of half-heard ideas
while
I roam, hourless,
over the mornings and afternoons
of possible lives not lived
and possible patterns
of impossible sciences