UV Fluorescence in Nature

[pisum]

@pisum

in my area, the only natural thing that i’ve discovered that fluoresces with intensity on par with manmade materials are some millipedes (especially their legs), which fluoresce a bright bluish green. lichens are a distant second in terms of intensity, though they probably have the largest diversity of colors – yellows, oranges, blues, greens, and even reds. next in intensity are some of the fleshy caramel-colored mushrooms in my area that fluoresce green, and this is on par in intensity as the red from chlorophyll. there are other things that fluoresce, but they tend to be less common or tend to be relatively small structures / relatively inconspicuous.

since then, i’ve discovered that rats also fluoresce about as brightly as some of the duller lichens.

some examples from my observations:

• millipede: https://www.inaturalist.org/observations/164140187
• rat: https://www.inaturalist.org/observations/164137122
• lichens: https://www.inaturalist.org/observations/18442347
• crust fungus: https://www.inaturalist.org/observations/164296601
• aphids: https://www.inaturalist.org/observations/76016696

@jnstuart

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.