Iran Press/ Sci & Tech: On a muggy spring night in 2016, the chemist Bernd Schöllhorn was tromping alone through a forest in northern Vietnam. Into the inky darkness, he raised a black light—and saw an extraordinarily bright shape winking at him in eerie shades of yellowish green.
“I thought it was somebody else,” Schöllhorn, a researcher at the University of Paris, said. But when he cut his own light, the stranger’s torch instantly extinguished as well. Schöllhorn pushed his way through the vegetation until he reached the source of the glow: a geometric, open-combed nest of a paper-wasp colony, the Atlantic reported.
“It was just incredible,” Schöllhorn recalled. Bathed in ultraviolet rays from his flashlight, the nest looked as though it had been dipped in a vat of highlighter ink, so bright and Day-Glo green that the inches-wide structure was visible from some 60 feet away. The wasps’ home, Schöllhorn realized, was fluorescing, as though prepping for an entomological rave, and he had no idea why.
Over the next several years, Schöllhorn and his colleagues searched for paper wasps in other parts of Vietnam, then in France and French Guiana, until they’d found nests from six different species in the genus Polistes. When fed a steady stream of ultraviolet rays, all of the nests glowed, each with a bit of regional flair: The four from Vietnam all pulsed in green, while the other two, from Europe and South America, were a more muted teal-ish blue. “Finding this in so many species, and across three different continents, is remarkable,” Swanne Gordon, an evolutionary biologist at Washington University in St. Louis, who studies insect signaling and wasn’t involved in the study, said.
The wasps themselves didn’t light up; neither did the topmost parts of the nests, constructed out of chewed-up wood (hence the “paper” moniker). The glow, the researchers found, came from a layer of silk stitched across the openings of the hexagonal cells at each nest’s base.
Scientists hadn’t pinpointed this silk as fluorescent before. Its primary purpose is to cocoon young paper wasps during their metamorphosis when larvae “dissolve their bodies” and reform themselves into adults, Sara Miller, a paper-wasp expert at Cornell University, told me. What’s inside the sealed cell is “really like a bag of mush,” Miller said. The larvae excrete silk out of a gland, and it shields the pupa from the ravages of reality—predators, pathogens, harsh weather conditions—much like a chrysalis protects a butterfly-to-be.
In the light of the forest, when viewed with human eyes, paper-wasp silk appears whitish or yellowish and is decidedly matte. But when fed ultraviolet light in the lab, the string-like fibers convert those rays into a fluorescence funky enough for an ’80s aerobics ensemble.
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