This episode is sponsored by Nautilus.   Go to Nautil.us/microcosmos to  receive 15% off your membership.

Hello, and welcome. You may have noticed that I am not one of  your regular hosts, and you are correct.

My name is Sarah Suta and you can  normally see me over at Bizarre Beasts,   but I heard that James, our master of microscopes,   had found something a little more macro  than usual and I wanted to take a look. I actually spent a good number of years looking  through dissecting microscopes at everything   from beetles to mosquitos, and I'm excited to see  what he found at an even greater magnification. Whenever we venture together  into the microscopic world,   as we often do on this channel, we never fail to  find both beauty and mystery in equal measure.

It's pretty much the only guarantee we have  when we point our microscope at a new sample. We don't know exactly what we'll see, but we know  it will leave us enchanted and full of questions. And the particular beautiful  mystery that we’re exploring   in this episode came to us via an unlikely source: a gang of ruthless cats… Let me explain.

See, a little while ago, James found  himself with a bit of a problem. He was keeping some wheat grains at  home to use as food for the microbes   that he cultures and films for our enjoyment. But before he could feed the grains to his  microbes, they became infested with the larvae.. of moths.

And while James worked to find the infestation,   his pet cats took it upon themselves to  deal with the situation in their own way. What you’re looking at now, bursting  with color like the northern lights,   are the wing fragments of some moths  that were slain by James’s cats. Because what does a microscopist  do when they find themselves with   an unexpected abundance of moth wings?

Well, you guessed it, they place  the fragments under a microscope   and attempt to reveal their secrets, of course. But what could be that complex or enigmatic  about something as everyday as a moth wing? It turns out, the wings of moths contain many  secrets that science has yet to fully explain.

Like, for example, the reason behind this  mesmerizing fluorescence unfolding in front of us. After all, you would be forgiven for generally   thinking of moths as rather  drab, as far as insects go. They’re not the most vibrant or  dazzling of critters to our eyes.

But it turns out that perception is more a result   of the limitations of our sight  than of their actual appearance. Because, under ultraviolet light, the  wings of these moths glow like an aurora. Both how and why this happens,  no one is honestly entirely sure.

Perhaps by exciting the wings  with high energy UV light,   their scales release fluorescent  particles into the water of the sample. These particles absorb UV and re-emit the  energy as visible light in the form of   vivid greens and oranges, allowing us to glimpse  the hidden beauty and vibrant colouration that,   under normal circumstances,  would be totally invisible to us. And, because the wing scales themselves  are hydrophobic by nature, the water   bursts with mists of fluorescent particles,  resulting in the waves of light we see here.

Another idea is that the wing scales  have some sort of innate UV reflection   or absorption properties, and what we’re  seeing are cones of light reflected by the   deforming nanostructures that are  responsible for those properties. See, it might be surprising to learn  that the overlapping microscopic   wing scales of moths and butterflies are  actually one of their defining features. Their scientific name - lepidoptera - is  a reflection of this characteristic trait,   it literally translates to ‘scaly wings’.

You might have even noticed this before,  if you’ve ever held a butterfly or moth,   they might have left behind  a fine powder on your hand. That powder is made up of hundreds  or thousands of these wing scales,   which we’re looking at right  now at high magnification. And the intricate, complex  nanostructures that line the   scales of their wings have been found  to have some interesting advantages.

For example, they play very strange  roles in their struggle for survival. Some species possess elaborate nanostructures  on their scales that interact with sound,   rather than light, providing them with a  form of sophisticated acoustic camouflage. For tens of millions of years, they’ve  been targeted by echolocating bats that   zero in on prey by bouncing  soundwaves off their bodies.

So, in response, the wing scales of  some moth species have evolved to   absorb these soundwaves, cloaking their  acoustic signature from unfriendly ears. Perhaps the wing structures we’re looking at now,  which interact with light waves, also evolved   for a similar defensive role in this species,  scattering light as a means of visual camouflage Or dazzling and obscuring the sight of potential  predators that can perceive certain wavelengths. Though, unfortunately for these particular  moths, it clearly doesn't work against cats… But predator avoidance is just  one of many possibilities.

Lepidoptera are an ancient and diverse  bunch, and their scaly wings are adapted   for a range of functions that we’re  only just beginning to understand. Some seem to use their UV reflecting  wings not to hide or confuse,   but the total opposite - to communicate. Like many other insect groups - but  unlike us - the eyes of lepidopterans   are exquisitely sensitive to the UV  part of the electromagnetic spectrum.

It’s the reason why researchers and  hobbyists will often collect them by   shining a UV blacklight against a sheet of fabric,  drawing in a range of species from far and wide. And various lepidopterans are thought to  use their UV perception and manipulation   abilities to signal amongst each other  for mate attraction, species recognition,   and other secret messages we  can only guess the meaning of. So maybe the aurora we’re gazing at is more like  fragments of a language that we can’t decipher,   brimming with information that  only other moths can comprehend.

But the truth is, we simply don’t know. For now at least, the beautiful mystery   of this moth wing light-show  reveals just one clear message: we still have so much left to learn. Thank you for coming on this journey with us as  we explore the unseen world that surrounds us.

And thank you to Nautilus  for sponsoring this episode. Nautilus is the science magazine that brings  the wonders of the universe to your fingertips. In a world of complex ideas, Nautilus  simplifies science so everyone can understand.

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You can become a member at the  url on the screen and embark on   a journey that will expand your  mind and ignite your curiosity. Memberships to Nautilus seldom go on sale,   but if you go to Nautil.us/microcosmos right  now, you’ll receive 15% off your membership. Those names you’re seeing on the screen  right now are some of our Patreon patrons,   and they are the reason that this show can exist.

If you’d like to join them in  supporting Journey To The Microcosmos,   you can go to patreon.com/journeytomicro to  get weekly wallpapers and monthly uncut videos If you’d like to see more from our  Master of Microscopes, James Weiss,   you can check out Jam & Germs on Instagram. And if you’d like to see more from us, there’s  probably a subscribe button somewhere nearby.