Spineless Samurai

When the annual cicadas emerge each summer their tymbals vibrate at arboreal drumming circles all over town.  The beats bounce and reverberate against hard city surfaces; during a crescendo, I swear I can feel the buildings and sidewalks pulsing like wings, like a heart. Yet, despite the percussive nature of this invertebrate orchestra, to my ears the cicada’s summer song evokes the kokyū—a traditional Japanese string instrument played with a bow.

This may be due to the fact that I imagine cicadas as miniature ronin, masterless six-legged samurai, stoic and single-minded, clad in intricately constructed armor of lacquered plates and scales. Of course, several beetle species call to mind this 12th-century warrior class, and I’m not the only one to see the resemblance. Rhinoceros beetles (Allomyrina dichotomy), for example, are known in Japan as a kabutomushimushi, the Japanese word for insect, and kabuto, which refers to the helmet worn by samurai (and the inspiration for Darth Vader’s visage).

It don’t know if it’s an example of the sincerest form of flattery or an unconscious imitation, but biomimicry—biological features or processes used as inspiration for beneficial products and practices— is an old technique that’s experiencing resurgence. Humans have long taken cues from the successful strategies of other animals. Indigenous cultures incorporated the characteristics of nonhuman animals into hunting tactics and rituals; composers have used all manner of musical instruments to simulate birdcalls and other nature sounds; superheroes like Spider-Man and Batman are pretty shameless about co-opting the special powers of their totem animals.

Then there’s warcraft. It’s hard to miss the resemblance between certain insects and the body armor worn by human warriors. From my perspective, there’s a natural synergy between invertebrates, who need a rigid external sheath for support and protection due to the absence of an internal skeleton, and Homo sapiens, who need prosthetic exoskeletons to protect our vulnerable bodies from the increasingly deadly technology imagined and fashioned by members of our own species—first flint arrowheads, then copper maces, bronze spears and daggers, iron javelins and swords, cannons and shrapnel, steel rifles and handguns, and eventually weapons that make any kind of armor irrelevant.

Chemical warfare is common in the insect world, and humans have readily adopted the same strategy against both macroscopic and microscopic opponents. In human enterprises, poisons do generally deliver short-term success; however, the initial win is usually followed by long-term health and environmental losses. This is particularly true when chemistry is used against presumed enemies with high reproduction rates… for example, insects and bacteria.

In most biological populations, there will usually be at least a few members strong or lucky enough to survive the application of toxins. Those individuals become the progenitors of the next generation, passing along their protective genetic code and, over time, rendering the chemical weaponry powerless. That’s how natural selection produces organisms well suited to their environment, and that’s why chemical deterrents always have a limited shelf life… against insects and bacteria, anyway. Less than 150 years after the introduction of antibiotics, hospitals and medical personnel are fighting resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and multi-drug-resistant Mycobacterium tuberculosis (MDR-TB), and attempting to do so with a limited alternate arsenal.

As a result, biomimicry is shrinking to nano-scale. Researchers are investigating new ways to protect human bodies from bacterial enemies, and certain insects have proven to be adept at mechanical antibacterial warfare. Think samurai on a microbial level.

In 2013, a team of researchers from Australia and Spain discovered that evolution has armed the clanger cicada (Psaltoda claripennis) with an elegantly simple defense against infection worthy of a kendo master. Clanger wings are covered with nano-pillars—aka tiny spikes.

Initially, it was assumed this pointed texture worked like a bed of nails—a hapless bacterium lands on the wing, stretching and sagging into the crevices between the spikes, and as gravity does its thing the pathogen’s skin tears, rendering it incapable of reproduction. Earlier this year, though, a group of Australian and Nigerian researchers proposed that truth is, once again, stranger than fiction… or at least as inventive as a movie villain.

Bacteria adhere to surfaces and each other by secreting finger-like structures called extracellular polymeric substances (EPS). These natural polymers allow the organisms to form biofilms on plant roots and fruit, fish and boat hulls, teeth and gums, plumbing pipes and medical catheters, even hot alkaline spring waters and glaciers—in other words, nearly any surface we know of except a nano-textured insect wing.

If the bacteria on a clanger cicada wing would stay put, they would likely deform but survive. If they move, though, those pillars subject the EPS to shear forces, ripping the external membrane and causing the bacteria to deflate like a balloon due to fatal leakage of the cell’s contents.

Regardless of how these nano-textured surfaces (NTS) kill, their potential as models for developing chemical-free, non-toxic antibacterial materials is undeniably exciting.  One of the first proposed products to utilize NTS was a coating that could be applied to countertops, doorknobs, railings, bus straps, subway poles, sinks, commodes, and even money. An Australian manufacturer of medical implants has acquired the patent, seeing potential for using this technology to reduce the chance of post-surgical infection. Since the killing mechanism is mechanical, devices coated with nano-textures could bypass the clinical approval processes required for chemical treatments, reducing the time and cost to bring these products to market.

Additional research has revealed that clanger cicadas aren’t the only winged insects armed with antibacterial nano-patterns, nor are they the most efficient.  The cicada’s NTS only kills gram-negative bacteria, but the wings of a fiery skimmer dragonfly (Orthetrum villosovittatum) have an NTS that is equally effective at killing both gram-negative and gram-positive pathogens. 

The nano-scale needles formed by black silicon have been tested in the lab and appear to have antibacterial properties similar to those of dragonfly wings. However, scientists aren’t yet sure why nano-patterned wings provides such a powerful defense, or how to replicate it for commercial use. That should come as no surprise given the nature of warfare, on any scale. It’s the Way of the Sword, and a samurai never reveals all of his secrets.

Every summer, people complain about cicadas but if insect wing nano-pillars become the next penicillin they may change their tune. Personally, I find the droning soundtrack soothing. I like knowing that, aided by sodium-yellow streetlights, spineless samurai are keeping watching through the night. Their kokyū lullaby floats past the gingko tree leaves, slips through my window screen, and into my dreams.


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© 2018 Next-Door Nature. First published at the Center for Humans and Nature’s City Creatures blog.  Reprints welcomed with written permission from the author. Thanks to the following photographers who made their work available through the Creative Commons license: Boaz Ng, Walters Art Museum, NFG photo, Mike BitzenhoferPaul Balfe, and tami abigador pearson.

City Creatures Guest Post

Looking for even more Next-Door Nature? Check out my guest post on the Center for Humans & Nature blog:

Summer Soundtrack

The eastern gray treefrog is one of many performers in nightly summer concerts.

The eastern gray treefrog is one of many performers at nightly summer concerts.

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One of my favorite things about summer is the free outdoor concerts. I’m not talking about local bands that occasionally perform from the park gazebo even though they can be a pleasant accompaniment to my evening dog walk. No, nothing says summer like the insect-amphibian jam sessions that take place almost every evening.
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I’ve moved quite a lot in my life and have been delighted to learn that each place I’ve lived long enough to grow accustomed to—six U.S. states and a Scandinavian country—has a timbre and cadence all its own, distinctive to that specific habitat in a certain continent on a singular planet in an expanding universe. It’s the soundtrack of home, wherever home may be at that particular time in field cricket 2 by Jimmy Smith, CCLone’s life.
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The musicians start warming up as the light begins to fade. They’ve been playing the same basic tune since I was a child so I immediately recognize the overture. By 7:00-7:30p the instruments are tuned and ready to swing.
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Field crickets (Gryllus spp.) establish the beat with their forewings, kind of like a finger-snap that varies from cool to hot depending on the atmosphere.
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Common true katydids (Pterophylla camellifolia) shift the accent…
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common meadow katydid by Rachid H, CCL… and the common meadow katydids (Orchelimum vulgare, not as common as the name implies) chime in with a bit of lawn-sprinkler syncopation.

 [you might need to boost the volume a bit on this one]

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Before long, the dog-day cicadas (Tibicen canicularis) are stealing the show.
dog-day cicada by Roger Engberg, CCL
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As the evening progresses, though, the cicadas and other insects cede the stage to the second act—the frogs and toads… possibly because these headliners have been known to devour the opening act!
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The band is made up primarily of horns and percussion. This isn’t jazz—there’s not much in the way of improvisation and the musicians don’t really take turns letting one another shine during a solo. It can be difficult to identify the featured players, in part because the cast keeps changing; there are fair-weather performers, some northern cricket frog by Andy Reago and Chrissy McClarren, CCLhave stormy temperament, and others don’t like to travel far from their favorite watering hole. Still, there are some easily recognized voices.
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Northern cricket frogs (Acris crepitant) step in to set the pace abandoned by their namesake insect. I’ve seen their call described as pebbles bouncing against one another but to me it’s a metal cabana—chain wrapped around a wood cylinder and shaken, not stirred.
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The American toad (Anaxyrus americanus) is a minimalist; not much complexity but the sustain on that single trilling note is impressive.
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green frog by Matt Reinbold, CCLThe green frog (Lithobates clamitans), on the other hand, is a true traditionalist—no electric bass for this fellow, or even an upright acoustic. Listen carefully and you’ll hear his homage to a single string and washtub.
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Tiny boreal chorus frogs (Pseudacris maculata) play plastic comb call-and-response…
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eastern gray treefrog by USFWSmidwest, CCL… and the gray treefrogs (Hyla versicolor) are in charge of the upper register. These little guys can blow, plus how about that vibrato!
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When the gang’s all here and lettin’ it rip the result is more cacophony than symphony—not everyone’s ideal night music but a lullaby to my ears.
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© 2015 Next-Door Nature—no reprints without written permission from the author (I’d love for you to share my work  but please ask). Thanks to these photographers for making their work available through a Creative Commons license (CCL) or Project Guttenberg License (PGL) (from top to bottom):  USFWSmidwest (eastern gray treefrog); Jimmy Smith (field cricket); Lisa Brown (common true katydid); Rachid H (common meadow katydid); Roger Engberg (dog-day cicada); Andy Reago & Chrissy McClarren (northern cricket frog); AllieKF (American toad); Matt Reinbold (green frog); J. N. Stuart (boreal chorus frog); USFWSmidwest (eastern gray treefrog). 

Goodness knows

Caption (Photo: OakleyOriginals 2008 Creative Commons license)

For this intrepid youngster, a cicada is good for a smile on a hot August day.

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Kindergarteners swarmed around the khaki-clad naturalist, squealing with excitement, shouting out questions and jockeying for a better view. The adult volunteers on this field trip were a tougher audience.

“I’m glad they’re having fun but I don’t see why anyone should care about some bug,” one 30-something mom confided to another, adding, “What good is it, anyway?”

I overheard this question while visiting a nearby urban nature center but it’s just one variation on a theme I’ve heard throughout my life and career… a theme that opens the door to fascinating explorations of the ways human beings assign instrumental and intrinsic value to creatures great and small.  And I do so love engaging philosophical conversations.

My first, unfiltered instinct, however, is to hurl the question back at them like a boomerang: “What good are YOU?”

I catch myself—usually—before the words escape, gently reminding my outraged inner eco-warrior that choosing honey over vinegar improves our chances of winning both the battle and the war.

To successfully implement a honey-offensive, it helps to have an arsenal of sweet scientific research think-bombs at the ready. This is an arms race and, naturally, I’m always on the lookout for a chance to acquire the hottest new technology so I can blast misconceptions and prejudices to smithereens.

Imagine, if you will, my greedy glee when, last week, I stumbled on an amazing new trove of ammunition from a most unlikely source.

Theo's friend by Phlora 2007 CCLIs there a creature  more likely to inspire the value question than a cicada? (In those parts of the world where insects are not a significant source of protein in the human diet, that is.) How’s this for a life cycle? Hatch from your egg, drop out of your natal tree, dig in and spend 1—17 years (depending on your species) hanging out underground sipping root juice and metamorphosing through various awkward stages of puberty. Finally emerge from the soil, climb out of your skin one last time. Rest until your shiny new wings harden then hook up with a member of the opposite sex and get busy… or not. Depends on how long you can avoid being eaten by a squirrel, a bird, a dog or cat, a fish… and rest assured, you will be eaten at some point during those 1—6 weeks of halcyon summer days preceding your demise.  Unless you are transformed into a zombie slave by a cicada killer wasp (Exeirus lateritius) in need of a surrogate mother for its offspring, in which case you’ll still be eaten but it will take longer for you to die.

cicada killing wasp by Steve Krichten 2003 CCLOne could argue that if the nihilists are searching for a mascot, they need look no further than one of the 2,500   Cicadidae clan member species. Still, until the pointlessness of existence becomes a dominant meme in human culture even a potential poster-child gig is unlikely to satisfy a determined anthropocentrist who insists on asking, “What good is it? You know… for people?”

Turns out, Australia’s clanger cicada (Psaltoda claripennis, aka clear wing cicada) may end up doing quite a lot of good for people. Unintentionally, of course; insects aren’t known for their benevolence. But according to a recently published Biophysical Journal article cicadas may be an accidental ally in our battle against bacteria.

clanger cicada by Melanie Cook 2004 CCLChemical warfare is common in the insect world. Humans readily adopt the same strategy against both microscopic and macroscopic opponents (although, in most circles it’s considered verboten in human-versus-human conflicts). Funny thing about man-made poisons—they tend to deliver short-term success followed by long-term environmental headaches, especially when used against enemies with high reproduction rates. Insects and bacteria, for example. As a former defense secretary once said, though, you go to war with the army you have. We have chemicals. Lots of chemicals.

How refreshing, then, that according to a team of researchers from Australia and Spain, evolution has armed the clanger cicada with a vaguely medieval yet elegantly simple physical defense against infection.

Spikes.

Enough to make a punk rocker proud (and Vlad the Impaler SO  jealous). You see, clanger wings are covered in an array of sharply pointed nanopillars. When a hapless bacterium settles on this surface, it stretches and sags into the crevices between the spikes, like Jell-O on a bed of nails, until the cell membranes are shredded and the microbe is incapable of reproducing.

Scientists have already begun to investigate the potential of synthetic cicada-inspired materials. Think of it—in the not-too-distant future countertops, doorknobs, bus straps and subway poles, sinks and commodes, railings, surgical instruments and even money could be covered with a passive bacteria-killing surface that makes the ubiquitous hand-sanitizers obsolete!

Now, how could an invention like that possibly do a young mother any good?

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© 2013 Next-Door Nature—no reprints without written permission from the author (I’d love for you to share my work. Just ask first.). Thanks to these photographers for making their work available through a Creative Commons license: OakleyOriginals (smiling face, 2008); Pholra (kitten, 2007); Steven Krichten (cicada killing wasp, 2003); Melanie Cook (clapper cicada, 2004)