TERRY GROSS, host:

This is FRESH AIR. I'm Terry Gross.

Underneath the cow patties in the pasture and the monkey dung in the jungle, there's a miniature world of sex and violence. Dung beetles with fierce-looking horns are battling over female beetles, and my guest, Douglas Emlen, is studying them.

He's an expert on the evolution and development of bizarre or extreme shapes in insects. He's particularly interested in insect weaponry. Dung beetles have what he's looking for.

Lots of Emlen's work is in the lab, but he's also had some wild adventures collecting different families of dung beetles from around the world. Emlen is a professor of biology at the University of Montana. If you want to follow along, on our Web site there's a dung-beetle slide show and a video of two beetles battling. That's at freshair.npr.org.

Doug Emlen, welcome to FRESH AIR. Now I think it's fair to say that dung beetles wouldn't be most people's first choice of an animal to study. So what is unique about the dung beetle's armor that makes you so interested in studying them?

Mr. DOUGLAS EMLEN (Professor of Biology, University of Montana): There are a variety of things, and I guess I should first of all qualify that by saying they weren't my first choice of an organism, either. It's a hard thing to wake up in the morning and decide you're suddenly go out there and study dung beetles.

I started out trying to study some of the big rhinoceros beetles as a graduate student, and the project failed pretty spectacularly, and it was a biologist named Bill Eberhardt(ph) that took me under his wing after that failed project and said no, no, no. You're looking at the wrong beetles.

And he opened up this box, and it was full of all these little, tiny beetles that are the size of your pinky or even the size of an eraser on a new pencil. And he opens up the box, and it smells like horse manure, and I looked him, and I said those are dung beetles. There's no way I'm going to work on those things.

And he laughed at me at the time and told me I was a fool, and basically explained that for all the kinds of biology that I wanted to understand, genetics and behavior and diversity, these things were perfect. And since that time, to come back full circle to your question, the dung beetles have turned out to be an amazing system to study, and they've taught us so much about biology in many ways.

But you mentioned the weapons. The thing that first drew me to them is the spectacular diversity in their morphology. They have these incredible shapes, and most of the diversity in those shapes involves these weapons. And so for lack of a better analogy, these tiny, little insects - that again, as I said, are often the size of an eraser on a pencil, on a new pencil - these things are the insect equivalent of a bull elk or a male deer, and they have incredible weapons coming off of their bodies.

And you look across the species, and there's variation among the species. Sometimes the horns comes from the back of the head, sometimes from the front of the head, sometimes from the thorax, which is equivalent to sort of between your shoulder blades. Sometimes they're branched, forked, curved, straight. There's just an incredible variety of forms.

And I was interested as a biologist in how a little, tiny animal like that could strut around with these enormous weapons sticking off the side of their body and survive.

GROSS: You know what? It's kind of amazing, and I mean, not only do they have these weapons, like, some of them are like antlers. Some of them are like a rhinoceros horn. Some of them are like lobster pincers. But they also have, like, hair.

(Soundbite of laughter)

Mr. EMLEN: Many of the horns - you mean the beetles or the horns?

GROSS: Well, the beetles, and yeah.

Mr. EMLEN: They do, and some of the horns in some of the species tend to have hair. We see that more often in the rhinoceros beetles than in the dung beetles, per se, but very often the sides of these horns are adorned with thick rows of hairs, and it's really sort of embarrassingly unknown what those things do.

There's a good chance that they are sensory structures so that when a male locks with another male, fighting, they can tell where the horns of the opponent male are because they're distending or pushing down all these fine hairs on the surface of the horn.

But some people think that the hairs might actually have chemo-detectors. They may be good for smell or for releasing signals. We don't know.

GROSS: I can tell you one thing for sure. They're not fashionable.

(Soundbite of laughter)

GROSS: They are really creepy looking.

Mr. EMLEN: That's a matter of opinion. I disagree. I think they're fantastic.

GROSS: Well, they are fantastic in a creepy kind of way. Let me ask you to describe one or two of the types of dung beetles that you find most fascinating in terms of their form and shape.

Mr. EMLEN: Sure. So one of the species of dung beetle that we spent quite a bit of time studying is - has the species name Taurus, as in the bull, and it actually has a pair of long, curved horns that extend upwards and backwards from the head of male beetles.

So it's a big, curled set of horns, and when the head is tucked back against the rest of the body, the horns sort of wrap in snugly around the equivalent of the shoulders or the thorax. But when these males are fighting, they pull their heads forward, and they've got quite an impressive pair of horns.

And we've looked at these beetles in a variety of ways and looked at what they do with the horns and who has the horns and who doesn't have the horns and how the horns develop, and all kinds of questions coming from that basic oddity of their morphology - the fact that they've got these huge weapons.

GROSS: You want to describe another one?

Mr. EMLEN: Sure. So one of my favorite species, unfortunately it's not one that we've been able to study in numbers, but it's one of the most spectacular of these beetles, is a species that actually was illustrated in Darwin's book, his treatise in which he initially described the whole theoretical concept of sexual selection, the process of biology that myself and so many other biologists study.

And in this beetle, the beetle is a brilliant, iridescent green color, turning sort of shimmering from a green to a yellow to a blue and in some angles even purple. So it has this beautiful sheen to it. And the males have a long, curved pair of horns that come up from the head that are much longer than the ones in the species I just described to you. And they have a branch in the middle of them with a tine that comes off and points inwards. And then at the very tips of the horns, it swells outwards into almost a little plate, so beautiful branched, curved horns coming off of this species.

GROSS: So the purpose of these weapons, the horns and the pincers, are basically to fight off other guys for girls.

Mr. EMLEN: Yup.

GROSS: So, like, the male dung beetles fight each other over the available female beetles.

Mr. EMLEN: They do, they do.

GROSS: So does that mean - have you watched them fight?

Mr. EMLEN: Oh yes, yes, many times.

GROSS: Oh, describe what a fight looks like.

Mr. EMLEN: It actually looks like pandemonium. It was not what we expected at all. So these are dung beetles, the ones that we're talking about right now, and so what happens in these cases are these beetles are very good at smelling their food source, and they follow these odor cues into the food. And when they find dung of the particular species that they feed on, they often have to deal with hundreds, and in some cases thousands of other individuals that are coming in and piling into that same place and competing to carve up and use that food resource.

So what happens is the beetles go instantly underground. They go right beneath the food source, the dung pile, so to speak, and the females actually excavate these burrows in the ground, and the males guard the entrances to these burrows. And they have big teeth-like spines on their legs, and they lock themselves, they brace themselves against the tunnel walls and try to prevent rival males from getting into the tunnels where the females are.

The females - these are amazing insects because they have elaborate parental-care behaviors. The females will take pieces of the dung down into the burrows and chew them up with their mouth parts and process them and pack them together into these sort of balls, these little sausages of buried dung underground. And then she'll excavate a chamber at the end of that and place an egg in there. And that's essentially the full food resource, like an allocate of food for each one of her offspring. And she'll do that, lay an egg and then close in the tunnel and then build another one of these balls and then close the tunnel. And we've watched these beetles do this.

The females will make 50, 100 different trips down into the ground for every single one of these eggs that she lays. And during this time, the male is guarding that tunnel, keeping everybody else away and mating with the female absolutely as often as he possibly can. And other males come and challenge.

And the fights take place inside these tunnels. And they scramble, and they push, and they pry, and they twist. And we tried forever to figure out how it is, exactly, that they use these horns because we wanted to know why would one species have a straight horn and another species have a curved horn and another species have a branched horn.

And we were assuming that we'd be able to pick up intricacies in the nature of these fights that would tell us why one species had one shape or another, and we failed. The fights are just chaos. We filmed hundreds of them, and they're amazing things to watch, but there's nothing predictable or repeatable about them except the outcome.

Somehow or other, bracing and twisting and prying and pushing and pulling and trying to get the other beetle out of the tunnel, somehow, at the end of the day, the male that has the longest horns and/or the largest body sizes typically is the one who wins. And the smaller males get pushed out of the tunnels and leave and go find another tunnel and try to push their way into that.

GROSS: So they just use these horns to bash away at their competition?

Mr. EMLEN: Yeah, I wouldn't call it bash. I would say they more use the horns to block the tunnel. You've got essentially a round or an egg-shaped animal blocking a tunnel, and they're very strong. So you have a rival pushing itself past, and it seems that the horns, regardless of what precise shape they take, seem to function like bars of a jail cell. They sort of block - they make it easier for a male inside the tunnel to block it so that another male can't push past.

But it's not as simple as that because they don't sit still. They twist and push and pry. But they don't stab with them. They aren't able to puncture the armor of the rival males. So they don't actually get injured in this process, and they don't really bash each other either, but they definitely spar and twist, sort of strength contests, I suppose.

But there's a twist to this story, too.

GROSS: Yeah?

Mr. EMLEN: Which is that the biggest males have the biggest weapons, and these are the ones that are usually the most successful at guarding that tunnel and at mating with the female inside the tunnel, but there are small males in these populations, too, and they don't produce the horns.

And so these small males look much more similar to a female. They don't have the big antlers or the big weapons, and they don't fight over the tunnels, either. They have a sneak tactic, a satellite tactic. What'll happen is they'll work their way into a tunnel and try to stay there, but they get kicked out right away by bigger males. And instead of going from tunnel to tunnel to tunnel to keep trying, they stay after they get kicked out, and they dig their own tunnel right next to the main tunnel. And after they get sort of a centimeter or so down below the ground, they cut horizontally, and they can intercept the guarded tunnel beneath the guarding male. And sometimes they're able to sneak in, zoom down to the female, mate with the female and get out again before the guarding male has essentially figured out what's going on.

So you've got big males with weapons fighting, and little, tiny sneak males without the weapons sneaking into these tunnels on the sly.

GROSS: So the less macho dung beetles still find a way.

(Soundbite of laughter)

Mr. EMLEN: They try. I don't think that they're as successful as the larger, dominant males, but yes, they definitely find a way.

GROSS: Can you see the armor and the weapons with your naked eye?

Mr. EMLEN: Yes, but I've had some practice. I think the first thing - if somebody were to go out and look for this in their backyard, which is the other fun thing about this system is that these beetles live in so many different habitats and so many places that you'd be pretty hard-pressed to live anywhere where you couldn't go into a pasture or into the backyard and turn over a cow-manure pile and look underneath it and find some of these beetles. They're that abundant and that widespread.

So if you were to go out and look for these things yourself and tip over a cow pile and look at the dirt, maybe dig with a trowel into the first couple inches of the soil and turn it around, you'd find these beetles. They're often, in most habitats, certainly around most places in the U.S. - they would be on the order of half-a-centimeter to a centimeter long, and they're squat.

The beetles that I'm talking about with the weapons walk like little tortoises. They sort of jerk their way along. And you can pick them up and see the horns with the naked eye.

We often look at them under microscopes to take more precise measurements of these things, and we photograph them either using really good camera lenses, or sometimes scanning electron microscopes will take really good pictures of these things, as well. But you can definitely, for a lot of these beetles, pick them up out of the ground and look at them with a hand lens or with your naked eye and see these really cool weapons.

GROSS: My guest is Doug Emlen, a biology professor at the University of Montana. We'll talk more about his work studying dung beetles after a break. This is FRESH AIR.

(Soundbite of music)

GROSS: If you're just joining us, my guest is biologist Doug Emlen, and we're talking about his work studying dung beetles. And he studies them because he's interesting in insects who have armor, and a lot of dung beetles have really fascinating armor, horns and antlers and so on.

Now you've described these, like, you know, antler-like and branch-like weapons and armor and weapons that the dung beetles have, and they sound, like, really big compared to the size of the actual beetles. Aren't they kind of cumbersome to tote around? I mean, I know they need them to fight and to bar off the tunnels and prevent other males from getting in, but they also must really get in the way.

Mr. EMLEN: They do, and so to try to give you a sense for how much they get in the way, the analogy I like to use is that for some of these beetles, it would equivalent to you producing another leg and wearing it around on your head for your entire adult life.

GROSS: Wow.

Mr. EMLEN: That's the best analogy I can give you because when you - if you try to estimate how big these things are, in some of these cases the horn, the weapons, can be 10, 15, 20 percent of the body weight of the animal. That's a fifth of the total weight of the animal is allocated to this one thing.

And so it really is analogous to an extra leg on your head for your entire adult life, and it has to be costly. So we've used a variety of types of experiments to try to measure how costly it is, and we found, for example, if a male beetle puts a ton of resources into making a horn, it means that he has to stunt something else.

There's not enough resources left, in a sense, and so in some of these beetles, if they have really big horns, they have really small eyes. We found that in beetles that have horns on the back of their head, their eyes were 30-percent smaller as a result of having allocated everything to the weapons.

In another species, they actually trade off with the testes or with the wings. So there are costs associated with producing these big, bulky things.

GROSS: So what do these dung beetles say about evolution? What do you feel like you've learned about evolution from studying them?

Mr. EMLEN: Honestly I'd have to turn that on its head and say what haven't I learned about evolution from them. These beetles have taught us, and me in particular, an amazing amount of lessons, some good and some more frustrating. But the biggest question that I have been focusing on and that I think I've learned a ton from these beetles on has to do with the backdrop of animal diversity.

It's very hard to be an evolutionary biologist and not look around you and become sort of increasingly aware of the differences among animals that are out there. There's so much variation in the ways things act, the way they look, and it is sort of amplified, in a way, in these beetles.

The variation in shape, especially connected with these weapons, is truly stunning in this group of beetles. And so as a biologist, I'm obsessed with understanding where this diversity in form comes from. How did these big, gaudy structures arise, meaning what do the beetles use these for? How - you know, once we know how they're used in natural populations, we can ask questions like how did they evolve? Under what types of ecological or environmental circumstances are these weapons likely to evolve?

And then that leads us to the next question of why don't all these beetles have the same weapons? What is it about them or about their history or the ecologies and behaviors of these animals in the past that has caused weapon evolution to go one way in some populations and a different way in other populations - and for it to go in enough different ways in enough different species that we end up with the truly thousands of types of shapes and forms and locations for these weapons on their bodies.

And so there's sort of fundamental biological questions connected with animal diversity that we are tackling with these beetles.

GROSS: Although we've been talking about dung beetles and the kind of weapons that they have, you also study the rhino beetle, which is a much larger beetle. Let me read something from Wikipedia, and you can tell me if this is all true.

(Soundbite of laughter)

Mr. EMLEN: Okay.

GROSS: Yeah, we looked it up.

Mr. EMLEN: Good for you.

GROSS: And it says that rhino beetles are among the largest of beetles. They are popular pets in Asia. They are clean, easy to maintain and safe to handle. Male beetles are used for gambling fights since they naturally compete for female beetles, with the winner knocking the other off a log. And they're also the strongest animals on the planet in relation to their own size. They can lift up to 850 times their own weight. All true?

Mr. EMLEN: I believe so. The last statistic I don't have personal experience with, and I might argue that the dung beetles are actually stronger than the rhino beetles, but the rest of that is definitely true, and I'm actually holding a giant rhinoceros beetle in my hand right now.

GROSS: Yikes. I wish I could see it.

Mr. EMLEN: Crawling up my arm.

GROSS: Oh gosh. You're in a studio in Montana, and I'm in a studio in Philadelphia. So we're not seeing each other, but I wish I could see that rhino beetle. Tell me what it looks like.

Mr. EMLEN: I will describe it to you. This male is about, almost four inches long, and he's a rich…

GROSS: Wow, it's big.

Mr. EMLEN: …brown, almost a purplish to brown to almost black color with a nice sheen to it and sort of golden hairs along the margins of his body, and the most striking feature of him, surprise, surprise, given what we've been talking about, is that on his head, he has an enormous horn.

This is a big branch structure that actually looks surprisingly like a pitchfork that extends upwards from his head, and in the biggest of these males, that pitchfork, that weapon, can be almost as long as the rest of the body of these males.

He also has another horn that's on the shoulder blades, the thorax, that comes up and curls a little bit forward and splits into two tips. But the horn that we're most excited about is this huge projection from the male's head that, you know, if I'm sitting here looking at the head and the eyes, the horn is probably 10 times the length of the male's head, and it comes up and splits into a Y, and then each of the tips of the Y split again so that you have these four points or tines at the T to this horn.

GROSS: Wow.

(Soundbite of laughter)

GROSS: I just wish…

Mr. EMLEN: That's the horn. The beetles are four inches long.

GROSS: I just wish I were seeing it, wow. So…

Mr. EMLEN: They prickle as they climb up your hands, same idea as with the dung beetles. They've got teeth or points on their legs that they use to brace themselves in contests, and spines on the legs that they do the same thing with, and when they grab you, they can prick you a little bit with the spines, but otherwise they're completely harmless. They feed, as adults, on rotting fruit. We keep them on apples, and basically sliced applies is what they'll quite happily feed on as adults. And they wouldn't be capable of biting you, even if you tried to get them to.

And they are kept as pets, not here. This is a species that we import with permits from the United States Department of Agriculture and we have to keep contained. But in Asia, where these things are native, they're very common pets. In fact, I'm told that you can buy the larvae in vending machines, and you can get the diet for these things in grocery stores. And kids really do keep them as pets. They're fantastic pets, and they do fight.

They put them on bamboo sticks and battle the males and, I believe, gamble on which of the males will win. I haven't actually done that firsthand, but I've seen plenty of photographs of kids doing that.

GROSS: It sounds like the cockfighting of the insect world.

(Soundbite of laughter)

Mr. EMLEN: I think it is.

GROSS: Doug Emlen will be back in the second half of the show. He's a biology professor at the University of Montana. I'm Terry Gross, and this is FRESH AIR.

(Soundbite of music)

GROSS: This is FRESH AIR. I'm Terry Gross. Who knew that dung beetles living beneath animal manure could be so fascinating? Let's get back to our interview with Doug Emlen, a biology professor at the University of Montana, who's an expert on the evolution and development of bizarre or extreme shapes in insects. He's particularly interested in insect weaponry and dung beetles have what he's looking for. The males are armed with bizarre looking horns, which they use to fight over female beetles.

If you want to see what we're talking about, go to our Web site freshair.npr.org where you'll find a dung beetle fight show and a video of two beetles fighting. One of the things that amaze me, I guess, particularly about the smaller dung beetles, is that there's just like invisible world of - this world, that - that you don't know - that at least I don't know - is out there in which, you know, insects are like waging war with weapons and armor and competing.

Dr. EMLEN: And sneak tactics.

GROSS: And sneak tactics, yeah - all like, you know, for the love of a good woman.

(Soundbite of laughter)

GROSS: You know, to mate with a female. So there's this whole world of like sex and violence, you know that's kind of invisible to us and is even happening underneath like cow manure.

Dr. EMLEN: I love that fact about these beetles actually. That's one of my favorite things about them is that this whole story is unfolding in most people's backyard. So just to give you a feel that one genus of the dung beetles that we work on, so one sort of taxonomic grouping of these beetles, there are two thousands species already described.

GROSS: Wow.

Dr. EMLEN: Probably another thousand species waiting to be described. The center of diversity for that group of beetles is Africa. But they occur in all continents accept Antarctica. And they feed on just about any kind of dung you can imagine. I mean, pretty much if you can think of an animal that produces a decent respectable quantity of manure there almost certainly is a beetle in this particular genus somewhere that is specialized on feeding on it. So these battles really do happen everywhere, in every habitat I've ever seen.

On every continent or country that I've ever been to. And it's the same basic story - the weapons are different. Sometimes they're on one part of the body, sometimes on another, sometimes they're branched, sometimes they're curved. But the story is basically the same. They dig these tunnels under the ground. It could be rabbit dung or deer dung, or elephant dung, or giraffe dung or cow manure but the beetles are still going to fly into the food source. They're still going to dig a tunnel into the ground underneath.

The males are probably still going to fight over the entrance to that tunnel. I'll be willing to bet you there are small sneak males that are still going to try to get into that tunnel on the fly. And you have this whole interesting dynamic, rich, behavioral system, taking place underground in every one of these habitats, on every one of these types of food sources.

GROSS: Tell us about one of your greatest adventures searching for dung beetles around the world.

Dr. EMLEN: Sure. There actually are a number, you wouldn't think that collecting dung beetles would be that adventurous but the truth might surprise you. So we have taken dug out canoes into the lowland forests of Ecuador searching for beetles. And we've sloshed through flooded pastures with leeches and wallabies in Australia. But the most common source of sort of danger or adventure collecting beetles is actually bulls. And if you can imagine we spend a lot of time in cow pastures. Well there's a lot of bulls in these pastures. And I think I can say that I have been charged full out by bulls on five different continents now and treed by them on three.

So we even had one time where I was charged by a cape buffalo in Africa. We had permits to collect beetles in the Serengeti. And they don't normally like you to get out of your vehicles in the Serengeti but in this case they were willing to help us to try to get the beetles. And we had armed guards standing on the roofs of the vehicles spotting for us to make sure that the cape buffalo didn't get too close. And we were out there diligently poking away and trying to find the beetles in the Serengeti and they were calling out the distances - 100 meters, 90 meters, 80 meters, 70, 50 run. And they would - and we would grab everything and leap back into the vehicle and get past there without getting charged by the cape buffalo, too close for comfort. But yeah, that was probably the most hair-raising opportunity to collect beetles.

GROSS: Do the guards think you're kind of crazy risking - taking risks like this to collect dung beetles?

Dr. EMLEN: They do. I have to say that's one of the pleasant side effects of this type of an occupation is that I often have to go out into places and introduce myself to complete strangers, to ask permission to collect on their land or in this case to ask the guards if they'd be willing to help us collect in the Serengeti. And they always want to sit down and talk to you about where you're from and what you do. And you meet some wonderful people that way but I think - I think more than a few of them thought we are a little bit nuts.

GROSS: So you have traveled around the world collecting dung beetles. Have you ever been surrounded by more dung beetles than you cared to?

Dr. EMLEN: Yes. And that would definitely have been in Africa. There is no place quite like Africa for dung beetles. And we'd heard about the numbers of beetles that you can encounter but I until I actually saw it first hand it was pretty hard to imagine. So it was actually the same trip in the Serengeti where we had the armed guards and we were trying not to get charged by the cape buffalo.

We happened across elephant dung in the road, and I realize normal people don't do this, but we hopped out of the car and collected the elephant dung in a Tupperware bin and brought it back to the campground where we were staying that evening. And I remember with the bunch of the students we all had headlights on and we set out to the edge of camp and placed the elephant dung out on the ground to see what we could find. And I sat there with my clipboard, trying to take notes on the beetles that came in and the beetles started coming in faster and faster and faster.

And pretty quickly it was impossible to see anything because there were all buzzing and circling around our headlights and then a couple of minutes later they were starting to pour out of the sky so fast that I couldn't even take notes on my clipboard because my clipboard was covered with literally an inch of solid beetles. They were going down our necks. They were in our hair. They were in our faces and finally by the end, this sounds like an exaggeration, but it's not, it was as if somebody stood over us with a bucket full of beetles and poured it steadily out on top.

The beetles absolutely covered absolutely covered the elephant dung - tens, probably hundreds of thousands of them came within minutes and we were utterly overwhelmed.

GROSS: So different dung beetles feed on different kinds of dung. Now I understand in Australia they actually had to import a certain kind of dung beetle because they needed it and there weren't any anymore or weren't enough.

Dr. EMLEN: That's true. So Australia has an interesting and rich native fauna of dung beetles. So there's a number of native species that are there, many of which have really cool horns incidentally. But the problem that Australia had was that when they clear cut a lot of the forests to create space for cattle, which was an important part of the economic development in Australia, it turned out that all of the native dung beetle species were specialists of forests.

And none of their native species would cross that barrier and sort of move from the woods out into the open. And from a beetle's perspective out in the open in the sun and a pasture is a very, very different environment then in the shade of a forest and so they had this problem of tons and tons of cattle and just obscene amounts of cow manure and no native beetles that were bearing it. And so the cow - I've seen photographs of pastures in Australia that are literally cow pat, to cow pat, to cow pat as far as the eye can see - just nonstop.

And what happened was they started getting flies that were sort of pest flies that went ballistic in this food source and were driving everybody crazy. And so Australia did a really good job of researching this problem. They went to Africa and to Europe, and they researched dung beetle species and found species that only lived in pastures. And they had this test, I mean, they basically tried to only find species that would not go into the woods. They would stay only in the pastures. And they picked these species and they bred them in captivity and then they had to do all these sort of quarantine procedures to bring them into Australia.

And then they bred them in captivity in Australia and they did controlled releases of these beetles. And it's taken - it's been a success. They now have a number of species that are very well established that bury the dung in pasture habitats. And because they went for that extra step of incorporating the biology of these beetles and finding species that didn't go into the woods that the introduced species have not, as far as I know, replaced or driven extinct any of the native species.

GROSS: Now you have described how dung beetles live, you know, largely underneath dung patties but don't some dung beetles actually live on the butts of animals.

(Soundbite of laughter)

Dr. EMLEN: Yes. So, again the dung beetles have diversified incredibly and part of that diversity has to do with specializing on different types of dung or different types of food. And there are beetles in the same genus - the same group that we talked about, the 2,000 species worldwide - there are species that have been described that are specialists for either koala dung or sloth dung. And in these cases, these are animals that move very slowly and they bury their dung. They'll climb down to the bottom of a tree and dig a horn and bury their dung underground.

If you can be at the right place at the right time, that's fantastic. It's a great way to have your food, have it buried on top of you and have all your eggs develop without any competition because nobody else finds it. And so what these beetles do is they actually ride around on the animals and they have specialized hooks on their legs that help them cling to the fur and they cling basically near the rear end of these animals. And they ride with the koala or with the sloth and when these animals go to the bathroom they hop off, go lay their eggs and climb back on again and wait for the next time. So it is true. Dung beetles do some pretty amazing things.

GROSS: My guest is Doug Emlen. He is the biology professor at the University of Montana. We'll talk more about his work studying dung beetles after a break. This is FRESH AIR.

(Sounbite of music)

GROSS: If you're just joining us my guest is Doug Emlen. And we're talking about his work as a biologist who studies dung beetles. And he studies dung beetles because they have bizarre forms, because they have armor, they have horns and antlers and…

(Soundbite of laughter)

GROSS: …all kinds of surprising things. But my impression of the beetles that you study based on the enlarged photos that I have seen is that they look really prehistoric because of the antlers and the armor and the pincers and the, you know, the horns - all the assorted weaponry. Are they prehistoric? Do they date back to the same era as the dinosaurs?

Dr. EMLEN: They do. There's reasonably - well, so if you use the types of tools that I alluded to a little while ago to reconstruct the history of these beetles. There are a number of studies now that have come up with pretty solid dates for how old these groups of animals are. So the dung beetles that we talked about so far, we spent most of our time talking about the group of dung beetles that I said are 2,000 species in it, that genus or that group of beetles we think dates back about 40 million years.

But that group of dung beetles is related to other dung beetles that date back further than that. And those beetles shared a common ancestor with the rhinoceros beetles, maybe a 150 million years ago. And so we definitely are talking about groups of these horned beetles that go back as far as the dinosaurs. And there is fairly compelling evidence that they were dung beetles back then in the sense that there are fossil coprolite, or scat, from dinosaurs that have burrows in them that resemble the burrows that we see made by present day dung beetles.

So it's circumstantial evidence at the moment but the histories that we reconstruct using molecular evidence, or using the sequences of DNA, also suggests that these lineages of beetles go back that far. So yes, I'd be willing to bet that there were beetles digging around underneath the dung of Tyrannosaurus rex or many of the other dinosaurs, the ceratopsids is for example, which also have really cool weapons like triceratops and styracosaurus. I'll bet you there were dung beetles crawling around under there and I'll bet you that beetles had horns too.

They probably did something not too different from what they do in people's backyards today - dug tunnels into the ground and fought over those tunnels with their weapons.

GROSS: So you've studied these beetles and they're really fascinating. How tolerant are you of insects that we regard as pests? Like, if you have ants or cockroaches that you find in your home, are you going to be fascinated by them or do you - do you want to just get rid of them as soon as possible?

Dr. EMLEN: Here is where I'm going to get in trouble with the pesticide industry. I actually would never spray for those things in my house because teaching entomology has taught me a great deal about the neurological and carcinogenic side effects of many of the things that we use to kill insects. So, the answer is I love just about all kinds of insects although cockroaches are an interesting one. Even most of the entomologists I knew don't like cockroaches, although they have amazing diversity in their parental care behavior. There's species where they carry the young around on their backs.

There's species of cockroaches that have the equivalent of a pregnancy. They actually will nurse their young, their eggs inside their bodies until they hatch. So it's a long developmental period inside their bodies and then when they hatch they have glands on their body that they feed these young with, which is just like nursing in humans. So cockroaches do some interesting things. And no I don't kill cockroaches.

There are a few types of spiders that I will squash with a paper towel and that's only because there's a chance that they have a necrotic bite, a dangerous bite, and we've got young kids and I don't take that chance. So if it looks like a hobo spider, I'll squash it. Otherwise everything else in our house lives.

GROSS: So, let me ask you, you said that, you know, entomologists who study insects are more negative about cockroaches and other insects, so even entomologists don't like cockroaches. I certainly empathize…

Dr. EMLEN: I'm going to get in trouble for saying that…

GROSS: …they have my full support in this.

Dr. EMLEN: as I'm there are exceptions in everything.

GROSS: …but why do you think that even entomologists don't like cockroaches?

Dr. EMLEN: I shouldn't have said that. I'm already going to regret it. But I knew - I know several entomologists that they have not liked cockroaches. For one thing many, many people are allergic to cockroaches. They have - basically cockroaches developing in your house or in a building, shed their cuticle, their skeleton and their skin as the molt as they grow. And they also have (unintelligible) or feces that they produce and these have chemical residues on them that many, many people are allergic to. And, I mean, I hate to say this on record but you'd be hard pressed to find any building probably in this country that's not infested with cockroaches at some level or another. Certainly all public buildings, they're - it's impossible to keep these things completely gone. And what happens is then the shed pieces of cuticles and frass get picked up in the air duct systems of these buildings and dispersed around the buildings.

And a lot of people suspect now that may be a major trigger for asthma, one of the causes of asthma because so many people are allergic to or sensitive to cockroaches. I can tell you an anecdotal story about that if you'd like…

GROSS: Please.

Dr. EMLEN: …that is sort of - okay. It's peripheral to what we've been talking about but when I was an undergraduate, I was hugely influenced by a professor of mine, a biologist and entomologist named George Ichor(ph), one of the greatest entomologists I ever met. And I remember driving across the country with him when I was a college undergraduate. He was an advisor to me. I was doing research out at a place called The Rocky Mountain Lab in Colorado. And we had to keep going way out our way - this was in the late '80s, this is before there was a Starbucks on every corner and you can get really good coffee.

And he was fiercely addicted to caffeine - to coffee. And we'd have to drive way off the interstate to go find good coffee in that day. I mean, we'd go 45 minutes off our route to go find a place that had whole bean fresh ground coffee. And I remember giving him a really hard time because we were wasting a lot of travel time trying to feed his addiction because he need a coffee every couple of hours. And he finally explained to me he had to drink only sort of whole bean fresh ground coffee. And it was because of cockroaches. There's a point to this story which is that he found out the hard way from teaching entomology year after year after year, handling cockroaches - people used cockroaches as the lab rat for entomology labs - he got really badly allergic to them. So, he couldn't even touch cockroaches without getting an allergic reaction. And because of that he couldn't drink pre-ground coffee. And it turned out when he looked into it that pre-ground, you know, your big bulk coffee that you buy in a tin, is all processed from these huge stock piles of coffee. These piles of coffee, they get infested with cockroaches and there's really nothing they can do to filter that out. So, it all gets ground up in the coffee…

GROSS: Oh.

Dr. EMLEN: …and he was actually allergic to pre-ground coffee because of that sort of spin off from having handled them teaching entomology for all those years.

GROSS: Oh I don't know what to say, thank you for that marvelous insight.

Dr. EMLEN: You may not want to put that on the air.

(Soundbite of laughter)

Dr. EMLEN: For better or worse.

GROSS: Oh, that's really upsetting.

Dr. EMLEN: That is a true story. That according to this professor and how he related to me and we wasted many, many hours trying to find basically fresh ground whole bean coffee so that he didn't have to have an allergic reaction to the pre-ground.

GROSS: Is there any other evidence besides this one person that there's…

Dr. EMLEN: Oh, there is.

GROSS: Yeah.

Dr. EMLEN: This isn't my forte but I looked into it a little bit because I tell that story in my entomology classes. Technically speaking, if I'm not mistaken, the FDA regulates the percent by dry weight of food stuffs like this that can be ground insect parts and make sure that it doesn't end up being too much of the total.

GROSS: Thank you.

Dr. EMLEN: And it's small, it's a trace amount. Chocolate incidentally is the other one that - if you think of these huge piles of beans, of cocoa beans, all piled up that then gets ground up in to something we all love and eat.

GROSS: Glad I asked, okay.

(Soundbite of laughter)

GROSS: Well, Doug Emlen, thank you so much for talking with us about the beetles that you've been studying.

Dr. EMLEN: Oh thank you. It's been my pleasure too.

GROSS: Doug Emlen is a biology professor at the University of Montana. You can find a slideshow of dung beetles and video of two beetles in combat on our Web site freshair.npr.org where you can also download podcasts of our show. Coming up, a Detroit label that got started in the '60s, recorded soul music and wasn't Motown. Ed Ward tells the story of Westbound Records. This is FRESH AIR.

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