These Carnivorous Plants Glow Under Ultraviolet Light to Attract Prey

It’s long been known that carnivorous plants lure their insect prey in a range of ways: irresistible nectars, vivid colors and alluring scents that range from rose to rotten flesh.

But recently, a group of scientists at the Jawaharlal Nehru Tropical Botanic Garden and Research Institute in India discovered a previously hidden means of beckoning among the most ruthless of greenery. Some carnivorous plants, they discovered, lure insects to their death with a fluorescent glow invisible to the human eye.

Scientists believe that insects are attracted to carnivorous plants by the their odors and colors, but hard evidence as to what exactly lures the bugs to their deaths was previously unknown. In a stroke of serendipity, a team of scientists led by botanist Sabulal Baby put several carnivorous plants they’d been using for unrelated experiments under ultraviolet light, including Nepenthes khasiana, a rare pitcher plant native to India, and photographed what they saw.

“To our great surprise, we found a blue ring on on the pitcher rim,” Baby says. “Then, we looked at other Nepenthes species and the prey traps of other carnivorous plants, including the Venus flytrap, and we consistently found UV-induced blue emissions.”

Under normal light, these bright, glowing rims would look green to humans. But an ant—which can’t see red, but is extremely sensitive to blue and violet light—would see rings of blue florescence, the result of metabolic compounds in the plant that absorb UV radiation from the Sun and re-emit it as visible light. Putting the plants under a UV light in an otherwise dark room, as Baby’s team did, amplifies the effect, allowing humans to more clearly see the blue emissions.

To prove that these emissions were involved in the plants’ predation, the scientists constructed an elegant experiment. They monitored live pitcher plants in the field for a ten-day period, cutting them open afterward and seeing how many ants each one caught. Some of the plants, though, were painted with an acetone extract that blocks fluorescent emissions. It’s not clear exactly why the ants would be attracted to the blue light, but the results, produced several times and in several different locations, pretty clearly indicate that it’s the case:

Read more: smithsonianmag.com

You know this gives me an idea. I think I may go get a battery powered blacklight and grab my camera one night and take a walk through the woods to see what may show up like that. Living in Florida there are lots of tropical plants and if that goes well the next trip down to Central America I will do the same.

Anyway the article kind of makes it sound like they were screwing around with a blacklight and stumbled upon this little nugget which got them brainstorming.

Thank you for posting this! I never believed that it was a scent or pheremone. Simple reason being that a pheremone would not likely attract so many varieties of insects. UV spectrum on the other hand...

Nice find. I like these threads that you share on nature. Best of luck with your battery-powered blacklight experiment! I think one way to do it would be to get a riding lawnmower battery that's charged and hook up a 200 watt power inverter to supply the power to your blacklight. Then, just throw the battery and the inverter in a backpack with the blacklight plugged into the inverter. Should last you at least 4-6 hours if it is a decent battery.

reply to post by InFriNiTee


Thanks for the idea and I am glad you like the nature threads. As far as the blacklight though I think I can come up with something a bit less heavy. ATM I have a couple cold-cathode florescent lights in my computer case that do a pretty good job and they don't take much power to run. I had been thinking of getting some LED versions so I will probably experiment with those at some point.

I'd heard this before about flowers. They will have patterns or "guidelines" that only show up under UV light and point their pollinators straight to the pollen / nectar.

Neat!