Stand back, bedbugs: we have leaves!

And other recent highlights from the Ideas blog

A bedbug, displayed at the Smithsonian Institution National Museum of Natural History.
AP Photo/Carolyn Kaster
A bedbug, displayed at the Smithsonian Institution National Museum of Natural History.

Bedbugs are one of the persistent urban annoyances of our time, seemingly as quick to spread as the common cold, and impossible to eradicate without turning your life upside down. But at long last, hope arrives, in the form of a new study touting an old remedy for this insidious pest.

The study, which was published on April 10 in the Journal of the Royal Society and discussed recently on the Smithsonian’s blog, examined an unlikely counter-bedbug strategy: kidney bean leaves. The authors report that bean leaves have long been used to combat bedbugs in Eastern Europe, where afflicted homeowners scatter the leaves around their beds at night, the bugs crawl over them and get stuck, and then the leaves are burned in the morning.

In the current study, the researchers, from the University of Kentucky and the University of California, Irvine, used a scanning electron microscope to observe exactly why the method works—they found that kidney bean leaves are covered with tiny hooked hairs called trichomes, which pierce the legs of the bedbugs, holding them fast. The researchers used their analysis to build traps that mimicked the impaling action of the hairs, but they found that even their best designs were less effective than the real leaves at stopping bedbugs.


How is it possible that such a basic solution has been hiding in plain sight all this time? The authors explain that kidney bean leaves actually received a burst of attention in 1943 with the release of a study called “The action of bean leaves against the bedbug.” But they conjecture that in the chaos of World War II, and with bedbugs receding as a public health concern in the 1950s thanks to the flagrant application of pesticides like DDT, people forgot about the remedy.

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The researchers expressed hope that someone would be able to improve on their trap designs, but in the meantime, let kidney bean leaves shield you from disaster.

The spontaneous megacity

Every 12 years, tens of millions of Hindus travel across India to bathe at the confluence of the Ganges and Yamuna rivers and wash in the divine nectar of the gods. The event is known as the Kumbh Mela, and it is considered the largest migration of humanity on earth. For researchers interested in how cities work, it is also something else: a real-time experiment in metropolis building.

For this year’s festival, which ran from Jan. 14 to March 10, a group of about 50 Harvard faculty, staff, and students traveled to the city of Allahabad in northern India to study what happens when a huge urban agglomeration arises and disperses so fast. The mela has a steady population of a few million people spread over seven and a half square miles of precisely organized encampment, and on a handful of main bathing days officials estimate the population may swell to nearly 30 million—making it, briefly, the largest city on earth.

Beginning last July, Rahul Mehrotra, a professor at Harvard’s Graduate School of Design, and his research team mapped the evolution of the temporary city. They lofted digital cameras on kites in order to get an aerial perspective of the mela’s development, and they mounted a camera atop a car and mapped several blocks of the festival’s road grid. In a research seminar he’s teaching this semester on temporary settlements, Mehrotra is studying the mela alongside other kinds of rapidly constructed, temporary settlements, including Burning Man and refugee and concentration camps.

AP Photo/Kevin Frayer, File
The Hindu faithful at the confluence of the Ganges and Yamuna rivers during the Kumbh Mela in Allahabad, India.


Other researchers collected data on disease prevalence, strategies for preventing stampedes, and the way prices for basic goods like tomatoes get set among the mela’s thousands of vendors. One of the problems they face trying to study this traditional festival is a very modern one: data overload. “The challenge for
researchers is to take this big phenomenon and reduce it to bite-size pieces,” says Tarun Khanna, a professor at Harvard Business School and director of Harvard’s South Asia Institute. Khanna is now working with India’s mobile phone providers to get access to cellphone records from the mela, which he says would be the largest database of its kind.

Over the next few months, the researchers will be trying to wrestle their mela research into something useful—both for improving the next mela, in 2025, and for understanding how temporary settlements operate anywhere in the world. They discussed their research at a symposium at Harvard this past Thursday and Friday and plan to release preliminary findings at a seminar hosted by the South Asia Institute in August. You can find updates on their blog, Mapping the Kumbh Mela, at

Elegant, until it rains

“You look really good in cardboard.” It’s not a compliment we’re used hearing, but it might become more common if more people saw Italy-based artist Chris Gilmour’s work. For the last decade Gilmour has created life-size replicas of a whimsical range of objects out of cardboard and glue: microscopes, roadsters, guitars, typewriters, drum sets. His work, which exhibited last month as part of the art festival SCOPE New York 2013, lends a palpable degree of nobility to the workaday objects he re-creates with it. The intricate detailing of each piece and the nostalgic brown finish invite you into Gilmour’s cardboard world—a place, maybe, where there’s winking magic in every object, and
people pray it never rains.

Kevin Hartnett is a writer who lives in Ann Arbor, Mich. He can be reached at