Is this correct: "…firefly luciferin (C11H8N2O3S2) is fluorescent, meaning it emits light after absorbing it or other types of electromagnetic radiation. [that's okay, but then…] In the case of fireflies, luciferin absorbs ultraviolet light – invisible to humans – which puts it in an excited energy state."

Fluorescence involves the simultaneous absorbing and emitting of radiation, so the fireflies could only glow by fluorescence while being illuminated by UV (i.e., in the sunshine when the glow would not be easily detected against the background lighting). [Phosphorescence would have allowed some delay, but unlikely long enough to keep glowing very long after sundown.] I think the article is here confusing two things - that luciferin as a substance IS fluorescent (so in the lab a sample will glow under UV illumination) and the particular type of luminescence that occurs in fireflies which has a chemical mechanism (and, as due to an enzyme in an organism, is classed as bioluminescence).

So, I think the otherwise fascinating article does include the correct information, but confuses matters by also including a mistaken claim about fluorescence in fireflies.

This is a topic with a lot of misinformation about (a number of websites claim quinine fluoresces as it contains rare earths!! - see https://science-education-research.com/would-you-like-some-rare-earths-with-that/) and there are a range of related phenomena which have sometimes been misnamed. (Phosphorus does not phosphoresce, but exhibits chemiluminescence!)

Perhaps Kit could do a follow-up on the wider topic?