11/01/2019

Moth Magic: Nature’s Underappreciated Night-Dweller

22:24 minutes

an illustration of 16 moths
Credit: Shutterstock

There are over 160,000 species of moths worldwide, and they come in all different shapes and sizes. For example, the Comet Moth, native to the rainforests of Madagascar, boasts vibrant red and yellow patterned wings, feathery antennae, and long swapping tails, thought to useful for distracting its bat predators. 

By comparison, most common North American moths seem boring and dull. While their butterfly relatives flit about the garden in daylight, moths are often found lurking around outside lamps at night. And they can be a nuisance—eating holes in your cashmere sweaters or natural fiber rugs. Even in popular culture they get a bad rap. We use terms like “moth-balled” to describe a cancelled project and “like a moth to flame” when we talk about a perilous situation.

a moth with its wings splayed out which are colorful like a butterfly's
A Chrysiridia rhipheus moth. Credit: David Lees

But do moths deserve the unflattering characterization of the mysterious, scaly-winged insect that haunts the night? Dr. David Lees, Curator of Lepidoptera at the Natural History Museum of London, certainly doesn’t think so. He joins Ira to set the record straight about moths by highlighting their astonishing diversity and usefulness.

Read an excerpt from Lees’ new book, Moths: A Complete Guide To Biology And Behavior.


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Segment Guests

David Lees

David Lees is a doctor of science and a curator of Lepidoptera at the Natural History Museum in London, United Kingdom.

Segment Transcript

IRA FLATOW: Even though there are more than 160,000 species of moths worldwide, the ones we see day to day in North America tend to do– well, they’re not that interesting to look at, right? Their wings are often drab and dull. And while their butterfly relatives flit around the garden in the daylight, we mostly see moths there lurking around lamps outside at night, trying to get into your house, where the light is.

They can be nuisance. They eat holes in your cashmere sweaters and wool rugs. I just discovered a hole in my sweater today from a moth. Now I’m wearing the sweater. But it’s just for this segment. So even in popular culture, they get a bad rap. We use phrases like “mothball” to describe a canceled project, or “like a moth to a flame” when we talk about a perilous situation.

So moths deserve– they deserve to be talked about much better than that. Moths don’t deserve this unflattering characterization. My next guest certainly doesn’t think so. And he’s written a book, a gorgeous book, that sets out to restore the moth’s reputation. So here’s a question for you. You have a question about moths in your neck of the woods or about some mysterious moth behavior you’ve observed? Give us a call. Our number, 844-724-8255, 844-SCITALK. Or you can tweet us at SciFri.

Dr. David Lees is curator of lepidoptera at the famous Natural History Museum of London. His new book is Moths, A Complete Guide to Biology and Behavior. Dr. Lees, welcome to Science Friday.

DAVID LEES: Ira, it’s a pleasure to be on your show.

IRA FLATOW: Great to have you. And the first question I have for you is I think what most people are wondering, how do you tell a moth from a butterfly? And what’s the difference?

DAVID LEES: Well, a moth is a non-butterfly scaly winged insect. So moths are actually, in popular conception, something rather like you’ve indicated, maybe something that is a bit mysterious and flips in from the night and maybe just brushes past your ear. And also, I’m sorry to hear that you had a hole in your sweater. They can attack us in ways that are not always endearing. But moths are actually an incredible group of organisms. And they– as you say, it’s the butterflies that we normally notice. But moths actually represent over 10 times the diversity of butterflies. And there is about 100– there’s actually 42 super families. And only one of those is a super family of butterflies. And they’re called papilionoidea. So there’s a fact for you.

IRA FLATOW: Wow. I’m Ira Flatow. This is Science Friday from WNYC Studios, talking with David Lees, curator of lepidoptera at the Natural History Museum in London. Why do moths have such a poor reputation when compared to butterflies? I mean, I– your book is beautifully written. I learned so much about the facts of them. And– did they have a common ancestor? Let me put it this way. How easy it is for me to tell if I’m looking at a moth or a butterfly? Can you give me a quick lesson?

DAVID LEES: Well, first, it’s not just my book. It’s written with my co-author Alberto Zilli, also at the Natural History Museum. So, repeat the question.

IRA FLATOW: I just wonder, if I’m out in my yard, how do I tell by looking at the moth or a butterfly– if it is a moth or a butterfly– is it– is there something I could say, aha, it has x, so I know it’s a moth or butterfly?

DAVID LEES: Yes. Yes. There are some rules of thumb. And one of the most commonly used ones is the antennae. If you look at the antennae of a butterfly, you’ve probably noticed they tend to have a club at the tip. Or at least some kind of thickening. And this works quite well for the butterflies that occurred in Britain. But you’ve got far more butterflies in the United States. And there are some butterflies, actually, which don’t have clubs at the tip. And that’s some day flying moths, as well, like the Zygaenidae, the Burnets, which have thickened tips antennae. So that’s not– it doesn’t work terribly well.

And in fact, you often, in fact, on seventh page, I think, there is an illustration of a moth from southwestern Madagascar, where the male has club tips and the female has fine antennae to the point at the tip. So it doesn’t work very well. But actually, there’s a more subtle character if you’ve got a magnifying lens. And you can manage to get a moth in your hand and handle it gently. There’s a tiny little bristle on most moths, which is a linking mechanism, actually. And the thing about butterflies is that they have lost this linking mechanism. Almost all of them have lost it, apart from a group of night flying butterflies, which were only just in 1986 realized to be butterflies rather than moths. They come from Central and South America.

That’s a tip that you’d need a lens for. Actually, you really– to answer the question what is a moth, you really need to know what is a butterfly. And as I mentioned, it’s just a single super family now once these night flying ones from South America were taken into account.

IRA FLATOW: That’s quite interesting. We’re going to take a quick break and come back and talk lots more with David Lees, doctor of science and curator of lepidoptera at the Natural History Museum in London, and author of the new book Moths, A Complete Guide to Biology and Behavior. And if you’re looking for a holiday gift, this is really an excellent, excellent find. And beautiful photos. Answers all kinds of questions and tells you stuff about moths I never knew, like, there’s a moth that drinks the tears out of a bird. We’re going to talk about that, Dr. Lees when we get back after the break. Stay with us.

This is Science Friday. I’m Ira Flatow. We’re talking this hour about the mysterious, scaly winged insects that haunt the night, moths, with my guest, Dr. David Lees, whose new book is Moths, A Complete Guide to Biology and Behavior. And Dr. Lees, you’ve mentioned this, I have mentioned it a couple of times, about the scaly nature of the wings. Why? Why are they built that way?

DAVID LEES: Well, all almost all moths and butterflies have got scales on the wings, but there are a few that have lost their scales just after the first flight or are more or less scaleless. They’re so transparent, in fact, that they’re almost invisible when they’re flying during the day. Of course, a lot more is going on at night. The scales actually turn out– it’s recently been discovered to not just insulate the moth– you probably have, maybe, some conception of a moth as a rather furry creature. Indeed, they’re rather cute, some of the moth pictures that you can see on the internet. But actually, it turns out that these scales actually are a kind of cloak. They disguise the moth against bats. The scales actually damp the sonar bats and make the moths a much more fuzzy target for their sonar.

IRA FLATOW: That is quite interesting. We have a tweet that comes in from Steve, wants to know– and we had phoners who want to know this, too– what is it about mothballs that moths do not like?

DAVID LEES: Well, actually, we used to use mothballs at one time in the museum. And people would comment on the stink as they came into the collection. But moth balls are not actually too good for human health. The usual substance in it is naphthalene, and it literally kills insects. It’s an insecticide. I can’t give you the chemical formula. But there are some things, like lavender, you can use to repel moths, that are much more eco-friendly.

IRA FLATOW: Let’s go to the phones. Let’s go to Brown Deer, Wisconsin. Hi, Deborah, welcome to Science Friday.

AUDIENCE: Hi. I once found a cecropia moth in my home. This is a couple years ago. I set it down, laid it outside, I covered it, and it was gone the next morning. I don’t know if someone in the household moved it. But did the moth die? Is it fair to say there’s a moth, if you find a moth laying on the ground? And this was huge. This is North America’s largest moth. Did it die? Or do you think that some bird came and eat it?

DAVID LEES: Was it big and black?

CALLER 1: It was brown and black.

DAVID LEES: Yeah. There is a moth called the black witch which is rather scary looking. But actually, if it was apparently resting in a living posture, it could be that in the morning, it got caught by a predatory bird.

IRA FLATOW: You did describe in your book a moth that plays dead, though.

DAVID LEES: Well, actually, this is an amazing thing that you can probably try it if you– most moths are perfectly harmless to handle. And there are some moths called [INAUDIBLE] which, if you turn it over, it will stick its legs in the air and appear to be dead. It’s kind of playing possum. And actually, there’s a few pictures like that in our book.

IRA FLATOW: You have the Monty Python theme in my head.

DAVID LEES: Yes, exactly. Legs in the air. Yes. It’s actually– it’s obviously not just intriguing to us because the moth appears to be pretty unwell, but it actually can fool a predator, because a predator might think it is just a horrible, dry hulk and not really worth munching for breakfast.

IRA FLATOW: Mm-hmm. I was telling you about some moths that actually live on other animals. You have in your book the sloth moth, and the moth on birds that drinks the tears of the bird.

DAVID LEES: Yeah. The sloth moth is rather extraordinary, because it comes down– it lives in the fur of sloths and then it comes down when the sloth has its weekly or less frequent ablutions. So actually, the larvae live on sloth dung. But this discovery of this bird eating moth was actually the first in the world. And I was actually involved in a way in its discovery. Or at least, discovery of the phenomenon.

What happened is that a contact of mine is a ornithologist, and he was studying, as, I suppose, nocturnal ornithologists do, the sleeping behavior of birds at night. And he took an amazing picture, which is in our book, of this huge moth sitting on the back of an endemic bird in Madagascar. And the moth, if you look more closely, it’s got a forked tongue, which is inserted– the proboscis is inserted between the membranes of the bird eye. And he observed this on two occasions. And on both occasions, the bird didn’t– as it were– bat an eyelid. So the bird was completely still. And I don’t know whether it was frightened or anesthetized. But he managed to capture one of these moths in a film capsule. And he sent it to me for identification. And it was an already described species.

But some scientists had been working on what’s called eye frequenting moths. So there’s a whole phenomenon of moths visiting eyes of mammals. But the thing is, in Madagascar, there’s– usually, it’s ungulates that are attacked, and in Madagascar, the only ungulates are introduced ones, that are actually cattle. So on one trip, I actually had to– I started looking at cattle at night. But the local people weren’t very happy about that, because they really prize their cattle there. So it was fantastic when we got this photo of the world’s first bird eating moth. It’s not really eating, the moth. What we think it’s doing is it’s feeding from the tears. It’s probably getting salts from the tears. And it’s the males that probably do this.

IRA FLATOW: Wow. And you say the birds sits still, let the moth do this?

DAVID LEES: Astonishing enough, in both cases, the bird was motionless. Apparently petrified to move. And if you imagine, you’re a bird sitting on a nice perch at night. It’s very dark. It’s risky to move. There’s snakes about that might get you. And so perhaps, it’s a strategy– or maybe the bird just doesn’t notice. But I think I would notice if there was a– so when I got this moth back, I was even more shocked to see, when we looked under the SEM and light microscope, we found that the proboscis had these barbs on it, backward pointing barbs. So I imagine if the bird gets attacked by one of these moths, it feels a bit bleary eyed in the morning. But the moth must have a way of escaping from the eye, as well. So since, it’s been discovered, several other bird eating moths have been discovered elsewhere in the world. Bird-drinking moths.

IRA FLATOW: That’s amazing. Let’s go to Sacramento, California. Hi, Katie. Welcome to Science Friday.

AUDIENCE: Hi. I really miss the Mexican Tiger Moth. I used to have them by my front door all the time. And I wonder, where did they go? I haven’t seen them for years.

IRA FLATOW: Any idea, David?

DAVID LEES: Shall I answer?

IRA FLATOW: Yeah.

DAVID LEES: Yeah. Well, I should– I tend to work with scientific names, so I don’t always know the species that you’re talking about. But if you lived in Mexico, I imagine you had a rich biodiversity around you. And one of the things that has come into the news, particularly earlier this year, is the massive decline in insects that’s happening all over the world.

IRA FLATOW: Right. Yeah.

DAVID LEES: So it may be that– many people commenting that they don’t see so many moths as they used to outside in the yard or attracted to their lights, the lighted window at night. And this may not just be a subjective opinion, because if you drive at night, most people don’t notice as many moths in the headlights as they used to. So there’s something going on with the declines of moths. And scientists are trying to figure out why.

IRA FLATOW: That’s really interesting that you brought up moths being attracted to light. Do we know why that is?

DAVID LEES: It’s a fascinating phenomenon. It’s somewhat self-defeating, really, for a moth to just flutter into a light and get burned by the light bulb. Or possibly eaten in the morning by a bird once it’s rested. And it’s– why would moths be attracted to light? Actually, since the introduction of ultraviolet lights, which, actually, moth collectors and surveyors use, you can get huge numbers of moths attracted to light. And almost all families of moths are attracted to light, apart from the day flying ones. And it seems like they were– well, there were several theories in the ’70s. It was thought that perhaps moths are attracted to the moon, which is, of course, natural source of light. But what happens on moonlit nights? And people tested this by flying up in a balloon to 2,000 feet up and one person saw a moth at this elevation at night.

But actually, there was another theory that moths are actually attracted to the pheromones of females. And that it’s the pheromones of females that are excited by the ultraviolet light so emit infrared radiation. And the antennae have tiny little sensilla which might resonate this infrared radiation. This is not thought to be as likely to be the case anymore. And the most popular theory is that they’re simply disorientated.

IRA FLATOW: Yeah.

DAVID LEES: They actually would normally navigate to a moon or stars or a distant light source, keeping the same angle to the light. And with our artificial, very bright, light sources, they are fooled and they keep turning inwards towards the light. And they just don’t seem to be able to escape very easily.

IRA FLATOW: Interesting. We asked our listeners to share their feelings about moths through the Science Friday VoxPop app. And they were excited about them. Here’s what Laura from Maryland and Bunches from Louisiana had to say.

AUDIENCE: Last year, we moved from the state of California to Maryland. And we knew moving here we’d see different kinds of creatures and bugs that we didn’t have in the state of California. But I never expected to see a moth that would make me change my mind about the way I feel about moths. This thing was even more beautiful than a butterfly to me when I saw it. It was just huge. The wings are so colorful. And it was on my garage door. And I am telling you, I have fallen in love with moths since I lived here. And I’m seeing all these different colors. I never thought it could be so beautiful.

AUDIENCE: Last week, I spotted an Io moth caterpillar. And as I work with kids, I was able to print off a picture of what this moth will look like once it’s been through the chrysalis process. They got to see the live io moth right before it dropped to form a chrysalis. And they got to see what it will look like.

IRA FLATOW: Now you have our listeners from the Science Friday VoxPop app. And they’re discovering, David, how beautiful moths are and getting their minds changed.

DAVID LEES: I encourage you to look through our book. And there’s some quite amazing photos in there, which I certainly hope will change your mind. Moths have some extraordinary patterns on their wings. Some– in fact, I sometimes wonder why women’s fashion normally has butterflies on the dresses and so on, but not moths. In many ways, moths are more artistic. There are moths that even have three dimensional patterns imprinted on their wings, patterns that create optical illusions in our eyes. So there’s a moth called the curled leaf moth that actually uses a phenomenon called counter shaking. It’s a trick of the light, and it looks like it’s airbrushed from dark to white on the top upper and lower part of the forewing. It gives the illusion of a gold leaf. It’s quite extraordinary.

But the second listener mentioned the amazing metamorphosis of moths. And we haven’t really talked about the caterpillars. But all four stages can be quite extraordinary. All have their separate adaptations. And in a sense, a caterpillar has a completely different ecology to the adult moth.

IRA FLATOW: Interesting. Our number, if you’d like to call us, is 844-724-8255. You’re listening to Science Friday from WNYC Studios. Talking with the David Lees, doctor of science and curator of lepidoptera at the Natural History Museum. And let’s see if we can– we have time for a call? Yeah, we have time for a call. Let’s take it. Let’s go to Jim in Rochester. Hi, Jim.

CALLER 5: Hi. My question– my question is, has light pollution played any effect on moths’ migration patterns? Or do moths have migration patterns?

IRA FLATOW: Good question. Do they migrate like butterflies?

DAVID LEES: They do. Actually, one of my first projects was to work on the migration of a moth called the sunset moth in Madagascar, which I’ve I never managed to see one, but it sometimes migrates in numbers almost to rival the monarch butterfly. And at night, there are clouds of Moths, actually, migrating. And it’s been discovered that you can actually track them by radar. So you can actually sometimes see these clouds by radar. And one wonders whether– it’s an interesting question that you’ve posed, whether the light pollution actually affects their migration. It’s not a question that’s, as far as I’m aware, anyone has probably answered. Certainly, light pollution is possibly one of the factors. You notice, if you go into urban environments, there maybe still plenty of food plants– trees and low growing plants around. But there are few moths when you get into urban environments.

IRA FLATOW: Is there a question about moths that you have yet to answer that you’d like answered?

DAVID LEES: Well, that one, yes. There’s a question for you which would be well worth addressing. How does light pollution actually affect moths and is it contributing to their demise in some way? Or are moths actually evolving and could they be– could they be becoming different in behavior? And this actually is– there’s one or two studies that have now been done. For example, small, urban moths. And it’s been discovered that using laboratory races of small, urban moths that once subjected to a kind of light regime, actually become more sluggish than ones in more natural conditions. So that the moths are actually just sitting about too much and they may be not serving their normal role, which includes services such as pollination.

IRA FLATOW: Well, we’ve run out of time, Dr. Lees. I want to thank you very much for taking the time to be with us today. It’s a great book. Dr. David Lees’ book is called Moths, A Complete Guide to Biology and Behavior. And you can check out some beautiful pictures of the moths, as well, from the book and an excerpt of from the book on our website at ScienceFriday.com/Moths. Thank you very much again for staying up late for us.

DAVID LEES: Thanks so much.

IRA FLATOW: You’re welcome.

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