Scorpions That Glow in the Dark

Saguaro National Park, Arizona–How do scientists find scorpions and certain other crawling animals in the dark, when a great many animals big and small are out and about in the desert night? They use a special light which makes the scorpions glow bright green, like the numerals on a watch.

Paul Marek, an entomologist at the University of Arizona, tells us in this video how researchers went out at night during the BioBlitz this past weekend to look for scorpions and other nocturnal animals.

Fluorescence is where you have emission of radiation or light that strikes an object which re-emits the radiation or light at a different wavelength, Marek explained. “Black lights” are used to illuminate scorpions, which re-emit the light as green light.

Scientists know why scorpions are fluorescent like this, because of a nitrogenous substance in its cuticles, but what’s not known with any certainty is whether there is any purpose behind the fluorescence (other than to make it easy for humans to find them in the dark). “It’s a really easy thing to,” Marek said. “You go out at night into the Sonoran Desert with one of these UV lights and … these scorpions light up and glow like a little star field on the ground.”


Photo courtesy of Paul Marek


The photos above, sent to me by Marek, show a scorpion glowing in a special light, compared with how the scorpion appears under regular light. Researchers aren’t quite sure if there is a reason why scorpions are fluorescent. Could it be a way for them to see one another in the dark?

The photos below are a selection of pictures made during the “inventory” to find nocturnal species in the Saguaro National Park BioBlitz. They were submitted by BioBlitz Photographic Ambassador Audrey Kanekoa-Madrid of Rainshadow Images.


Photo by Audrey Kanekoa-Madrid/


Looking for scorpions this way, Marek said, confirmed a number of different species of scorpions are present in Saguaro National Park. “The most common ones we found were the Arizona bark scorpion, the striped scorpion, and the Arizona hairy scorpion.” The bark scorpion and the striped scorpion are the scorpions that cause the most medical problems, Marek said, because they pack the most venom.


Photo by Audrey Kanekoa-Madrid/


Scorpions weren’t the only animals Marek and his team found in the BioBlitz of Saguaro. “We found some nice black widows, but what I didn’t know before is that their little spherical egg cases fluoresce. We also found some really nice big desert centipedes,” he said. It sounds like Saguaro is ready for Halloween!


Photo by Audrey Kanekoa-Madrid/
Photo by Audrey Kanekoa-Madrid/


Scorpions are an essential part of the ecosystem, Marek told me. “Scorpions are predators, so they feed on smaller arthropods, little cockroaches and flies … basically anything smaller than them … They keep herbivore populations down.”

Does anything eat scorpions? The southern grasshopper mouse preys on scorpions, Marek said. “They’re known as wolves in mice clothing. These little mice that actually bark … are like little ninjas. They go up and grab the scorpion, run around them, and can quickly chew off the tail of the scorpion, that has the stinger on it, so they can feast on the rest of it,” he said. Did the BioBlitz team see any of these ninja rodents during their field trip? “No, we didn’t see any of those, but the scorpions may have known about them,” Marek said.


Photo by Audrey Kanekoa-Madrid/

Read more about Paul Marek’s work here.

12418031_10153900711084116_8462971761216697621_nDavid Braun is director of outreach with the digital and social media team illuminating the National Geographic Society’s explorer, science, and education programs.

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Braun also directs the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship

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More than forty years in U.S., UK, and South African media gives David Max Braun global perspective and experience across multiple storytelling platforms. His coverage of science, nature, politics, and technology has been published/broadcast by the BBC, CNN, NPR, AP, UPI, National Geographic, TechWeb, De Telegraaf, Travel World, and Argus South African Newspapers. He has published two books and won several journalism awards. In his 22-year career at National Geographic he was VP and editor in chief of National Geographic Digital Media, and the founding editor of the National Geographic Society blog, hosting a global discussion on issues resonating with the Society's mission and initiatives. He also directed the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship, awarded to Americans seeking the opportunity to spend nine months abroad, engaging local communities and sharing stories from the field with a global audience. A regular expert on National Geographic Expeditions, David also lectures on storytelling for impact. He has 120,000 followers on social media: Facebook  Twitter  LinkedIn