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Bedbugs, Bean Leaves and Biomimicry

Health + Wellness
Bedbugs, Bean Leaves and Biomimicry

David Suzuki

Scientists often come up with new discoveries, technologies or theories. But sometimes they rediscover what our ancestors already knew. A couple of recent findings show we have a lot to learn from our forebears—and nature—about bugs.
 
Modern methods of controlling pests have consisted mainly of poisoning them with chemicals. But that’s led to problems. Pesticides kill far more than the bugs they target, and pollute air, water and soil. As we learned with the widespread use of DDT to control agricultural pests and mosquitoes, chemicals can bioaccumulate, meaning molecules may concentrate hundreds of thousands of times up the food web—eventually reaching people.
 
As Rachel Carson wrote in her 1962 book, Silent Spring, using DDT widely without knowing the full consequences was folly. She showed it was polluting water and killing wildlife, especially birds, and that it could cause cancer in humans. Her book launched the environmental movement but did little to change our overall strategy for dealing with bugs. Although DDT was banned worldwide for agricultural purposes in 2001, the chemical is still used to control insects that spread disease.


 
Recent research shows that widespread use of pesticides like DDT may have caused us to ignore or forget benign methods of pest control. Because the chemicals were so effective, infestations were reduced and there was little interest in non-toxic methods. But bugs evolve quickly and can become immune to pesticides. That’s true of bedbugs, the now ubiquitous critters that are showing up around the world in homes, hotels, schools, movie theaters—even libraries.
 
But a method used long ago provides an effective and non-toxic weapon against the pests, according to a U.S. study in the Journal of the Royal Society Interface. The authors looked into the once-common Eastern European practice of spreading bean leaves around a bed to control bedbugs. What they found was fascinating.

The scientists, from the University of California, Irvine, and University of Kentucky, wrote:

During the night, bedbugs walking on the floor would accumulate on these bean leaves, which were collected and burned the following morning to exterminate the bedbugs. The entrapment of bedbugs by the bean leaves was attributed to the action of microscopic plant hairs (trichomes) on the leaf surfaces that would entangle the legs of the bedbugs.

They discovered that after bugs get caught up in the hooked plant hairs, they struggle to escape, and in the process vulnerable parts of their feet are pierced by the hooks, permanently trapping them. The research focuses on a way to replicate this.

“This physical entrapment is a source of inspiration in the development of new and sustainable methods to control the burgeoning numbers of bedbugs,” the researchers wrote, adding that the method “would avoid the problem of pesticide resistance that has been documented extensively for this insect.”
 
Other research has literally dug up pest control methods that go back millennia. An international team of archeologists recently found evidence that people living in South Africa almost 80,000 years ago made bedding out of insect-repelling plants.
 
According to the journal Science, the research team found 15 different layers containing bedding made from compacted stems and leaves of sedges and rushes, dating between 77,000 and 38,000 years ago. One layer of leaves was identified as River Wild-quince, which contains “chemicals that are insecticidal, and would be suitable for repelling mosquitoes.” The archeologists also found evidence that people often burned the bedding after use, possibly to remove pests.
 
These are just two examples of what we can learn from our ancestors and from nature. Because natural systems tend toward balance, the fascinating field of biomimicry has developed to explore what nature can teach us. It’s aimed at finding “sustainable solutions by emulating nature’s time-tested patterns and strategies,” according to the Biomimicry Guild website. “The goal is to create products, processes and policies—new ways of living—that are well-adapted to life on earth over the long haul.”
 
Maybe the truest sign of human intelligence is not to learn how we can shoehorn nature into our own agenda, but to see how we can better find our own place in nature.
 
Written with contributions from David Suzuki Foundation Communications Manager Ian Hanington.

Visit EcoWatch’s BIODIVERSITY page for more related news on this topic.

 

A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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