#50: Dr. Brian Brown – Phenomenal Phorid Flies, Hyperdiversity, DNA Barcoding, and more

#50: Dr. Brian Brown – Phenomenal Phorid Flies, Hyperdiversity, DNA Barcoding, and more Nature's Archive


Today’s guest is Dr. Brian Brown, Curator of Entomology at the Natural History Museum of Los Angeles County. A native of Toronto, Canada, Dr. Brown did his undergraduate and masters work at the University of Guelph. During the latter, under the tutelage of well known entomologist Steve Marshall, Dr. Brown took up the study of the fly family Phoridae. This is a phenomenally diverse family of extremely interesting flies that, of course, we discuss at length today.

In 1990, Dr. Brown obtained his doctorate at the University of Alberta in Canada, followed by a postdoctoral fellowship at the Smithsonian Institution and University of Maryland. In 1993 he took up his current position in Los Angeles.

Today we discuss Dr. Brown’s work at the Natural History Museum of Los Angeles County – in particular, the scale and diversity of the collections, and the implications of that on the work that he does. 

We pretty quickly delve into the aforementioned phorid flies. There are potentially as many as one million species of these flies, but to give you an idea of the diversity and scale of the work, only 4,500 have been described to date. Yes, you heard that right! Dr. Brown discusses the challenges of having so few people studying such an immense diversity of species, and approaches involved such as DNA barcoding.

Even among the 4500 described species, there are many amazing natural history stories that we get into, ranging from the aptly named “Coffin Fly” to ant-decapitating phorids.

We weave in and out of many fascinating subjects, from research in the Amazon canopy, to surprising discoveries in Los Angeles, to invasive ant species.

You can find Dr. Brown through the museum’s website at nhm.org, on his blog at flyobsession.net, or his Phorid fly site at phorid.net.

This discussion was full of surprises and a lot of fun, and I hope that you enjoy it as much as I did.

Did you have a question that I didn’t ask? Let me know at naturesarchivepodcast@gmail.com, and I’ll try to get an answer! I’ll add these Q&As to my monthly newsletter, so if you aren’t already subscribed, go here. I promise, no spam. I share the latest news from the world of Nature’s Archive, as well as pointers to new naturalist finds that have crossed my radar, like podcasts, books, websites, and more.

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Dan Janzen, ecologist cataloging Costa Rican biodiversity

flyobsession.net – Dr. Brown’s blog

Natural History Museum of Los Angeles County

The Nature Conservancy – conservation charity recommended by Dr. Brown

Phorid.net – Dr. Brown’s Phorid resource

Rainforest Trust – conservation charity recommended by Dr. Brown

Music Credits

Opening – Fearless First by Kevin MacLoed

Closing – Beauty Flow by Kevin MacLoed

Both can be obtained from https://incompetech.filmmusic.io/


Transcripts are automatically created and only lightly edited, and are about 95% accurate. Apologies for any errors.

[00:00:00] Michael Hawk: Dr. Brown, thank you so much for making time today to talk.

[00:00:02] Dr. Brian Brown: It’s very much my pleasure, Michael.

[00:00:04] Michael Hawk: I’m really excited to learn about the natural history museum, your own research some of the specialties that you work on, but as I like to do, why don’t we start with, where did you grow up and how did you get interested in nature in the first. So

[00:00:20] Dr. Brian Brown: I grew up in Toronto, Canada, which sounds like it might be a really cool place for a naturalist to grow up, but actually it’s a city in a relatively impoverished part of our country in terms of the fauna. So I grew up always aspiring to better nature. I was always reading books about places like the tropics and the Southern us and so on.

[00:00:43] I got interested in nature just by kicking around. Vacant lots and soon to be paved over developments. And that’s what really strikes me about my childhood.

[00:00:54] Michael Hawk: you’d see these vacant lots, and it was just like a blank pallet in area to.

[00:00:58] Dr. Brian Brown: I was aware very early that it looked different to me than to most people. Most people saw vacant lot as empty land to be developed. And I saw it as a treasure trove of remaining biodiversity.

[00:01:12] Michael Hawk: and do you have any recollections of interesting things? It’s probably lots of interesting things that

[00:01:20] Dr. Brian Brown: One thing I remember coming home from school one day, there was some giant maple trees lining the road. They’re long gone now, of course, but there were these gigantic wasps called Merissa that are parasites. Grubs inside a beetle grubs inside trees. And they’re really big. They’re about oh six inches long with their long tails and they can bend their tails around and then down.

[00:01:48] And they drill through the wood in order to find the host beetle larva that they lay their eggs in. And I thought this was the coolest thing that I’d ever seen, but some of the kids that were walking along with me smashed them. That kind of attitude towards nature really annoyed me even back then.

[00:02:05] Michael Hawk: that’s it’s I had a discussion just last night, we were talking about fireflies and a similar topic came up. Now these six inches I, how much of that was tail.

[00:02:15] Dr. Brian Brown: Oh, good. Three quarters.

[00:02:17] Michael Hawk: And is that what they drilled with or tell me more about that.

[00:02:20] Dr. Brian Brown: So if they have a pair of sheaths, basically, and then a central ovipositor, actually the egg goes through and these sheaths catch on each other. And so they can slowly inch their way through the wood. It’s sharp and they’ve got recurved spines, so they put that sheath through and then they put their over, ovipositor through, and their egg gets super, super elongate as it goes through.

[00:02:46] if you can imagine one of these eggs sliding through this tiny tube to get into the beetle larva,

[00:02:52] Michael Hawk: So yeah, a lot of interesting adaptations there to make that all work. And I guess somehow they have to know that the beetle larva is in there and where it is. It

[00:03:01] Dr. Brian Brown: Yeah. So parasitoid searching behavior is something that’s a very hot topic and it’s a lot of interesting stuff has been done, especially with parasitic, wasps, not

[00:03:13] Michael Hawk: I know we’re gonna talk more about parasitoids as we go on through the conversation. So thanks for indulging me with that side story. , I guess my takeaway here is early on you recognize that you were interested in nature with these vacant lots. How did that then progress to taking it on as a career?

[00:03:30] Yeah.

[00:03:30] Dr. Brian Brown: I stayed interested in it, although I was relatively isolated in my scientific interest. Like I never met an entomologist until I went to college. So that was the first time that I’d ever met someone who studied what I wanted to do. I continued my interest in insects then got out of it for a while, played in the heavy metal band, discovered girls, that kind of stuff then got back into it in university and met some very inspiring professors and fellow grad students that got me going

[00:04:02] Michael Hawk: So fast forward to now your curator of entomology at the natural history museum of LA county, it’s big natural history museum. Connect a couple of those dots as to, to how you were able to get into that position.

[00:04:15] Dr. Brian Brown: well. I did my PhD at the university of Alberta, which is in Western Canada. And after that, I went to the Smithsonian for two years on a post-doctoral fellowship. So traverse the whole continent. And then right when the LA Rodney King riots were happening, I got. Called in for an interview for the job at the LA county museum.

[00:04:38] So I went all the way across the country again, and this position almost 30 years ago. it’s been a great career. It’s not quite over yet, but I haven’t regretted any of it.

[00:04:50] The thing about entomology is you can do a lot of it wherever you live, just because insects are everywhere. And they’re the most available form of wildlife for people, especially in urban areas. Just in our museum backyard or the garden, I should say we’ve gotten hundreds of species of insects in our, on again, off again, surveys that we’ve done there.

[00:05:11] You could get a thousand species in a backyard here in California, pretty easily. I think.

[00:05:15] Michael Hawk: Yeah. That doesn’t surprise me and listeners to the podcast have heard me talk about this before, where when. COVID started like so many people I still needed to get my outdoor fix. So I started paying a lot more attention in my backyard. I’d always paid a little bit of attention, but mainly to like the birds or the squirrels, or, the sort of backyard megafauna and there were two things that struck me very quickly in my backyard.

[00:05:39] And that was the diversity of spiders and the diversity of syrphid flies, which were really overlooked, by me anyway. And oh, I can’t recall how many different species of surf flies I’ve had in my yard eight or nine or 10, I think. And there’s probably more if I knew more where to look that I, maybe I could find more.

[00:05:59] But yeah, absolutely. It’s so much fun and you can see all of these things that. Say animal planet or discovery channel shows in terms of hunting styles and lifestyles in small scale, in your own backyard, which is just awesome. I think, tell me

[00:06:15] Dr. Brian Brown: Yeah. One of the easiest ways to increase the visible biodiversity of your backyard is to plant a lot of flowers. And of course, you’ll get those surfs or flower flies coming in and lots of native bees, as well as the introduced honey bees that are also occur here. And yeah, that’s the way to show off more biodiversity in your yard.

[00:06:36] Michael Hawk: what’s the day in the life of curator of entomology, like at a museum? I have no idea what you do day in and day out, but I know you also do research

[00:06:45] Dr. Brian Brown: You’d probably be really disappointed. I go into work and I, do some administration. I have a staff, I have some grants that I’m working on. That require my attention and I do research. Yeah. That’s a big part of my job. So as a curator, I don’t teach, we don’t have classes at any local university, although we are physically right across the street from USC.

[00:07:09] But yeah, I look at specimens of my insects, the things that I work on, which I’m sure we’re gonna talk about. We have some pretty sophisticated equipment for doing that, including a beautiful microscope camera setup that allows me to do stunning insect images and scanning electron microscope as well.

[00:07:30] Micrograph that allows us to look at very high magnifications at structures. So my goal is to try to make more of the hidden world of my tiny little flies available for everybody. The

[00:07:45] Michael Hawk: , by making your world of tiny little flies, more available to people, you mentioned some of the tools that you have are these based on specimens in your museum, or are these specimens that you are actively seeking and collecting at the.

[00:07:59] Dr. Brian Brown: specimens. I work on belong to a single family, just about entirely one family called the phoridae. When I first got to the LA county museum, we had half a drawer of phorids in the collection. Now we have, I don’t know, at least a thousand drawers of them maybe, I don’t know, half a million specimens.

[00:08:20] So we have built up an incredible resource of these flies. And so there’s enough for me to work on it’s enough for more than one generation of succeeding, entomologists to work on if they want to. So we have incredible collections at the museum and what you see on display at the museum for all types of organisms and subjects is a small portion of what we actually have in the collections.

[00:08:44] Michael Hawk: Yes.

[00:08:44] The scale that you talk about of all of these drawers of specimens really speaks to pardon the metaphor, but it’s the tip of the iceberg of the diversity in entomology. So that’s the thing that intimidated me a little bit about your title, because entomology is so huge and how can one person , curate all of these things and have a specialty.

[00:09:08] So I’m guessing you have support staff. And tell me a bit more about the scale and the hyper diversity that exists within the space.

[00:09:15] Dr. Brian Brown: Yeah. Most entomologists have to focus their work on one level. And the level we usually work on is the family level. So I, for instance, am an expert on the family phoridae. And I’m the only person in North America. Who’s an expert on the family Phoridae now. You consider how many people in Southern California are experts on one species of animal.

[00:09:39] For instance, the mountain lions, how many people are studying mountain lions in Southern California? Probably more than there are mountain lions. So I work on a family. That’s probably the second largest family of insects in the world. There could be, I don’t know, a million species of phorid flies. We’ve only described about 4,500 of them so far.

[00:10:01] You can see that the scale is just incredible and not only the scale of what’s to do, but how you’re going to deal with this in a practical way. Like when you work on a group I don’t know a group of birds, you have 20 or 30 species. Maybe you have to tell them apart at one site. In the tropics, we might have a thousand species of, phorid flies.

[00:10:27] How do you tell those apart? I mean, What practical way can you do that? You can’t keep a thousand images in your head. You have to have identification aids, like identification, keys. Maybe some people are familiar with them where you get a specimen and you look at your book and you say, okay, the first couplet says wings, black versus wings, yellow.

[00:10:52] Okay. So it’s wings black. You go to the second couplet and so on and you answer questions to narrow it down to what that thing might be that only works up to about, I don’t know, a hundred, 200 species after that. It’s just incredibly overwhelming. And you start getting so many exceptions to these giant generalizations.

[00:11:12] You have to make, to try and narrow the groups down that it gets almost impossible. Yeah, the working on hyper diversity is a big problem that we haven’t been able to tackle yet, but we will be tackling with new technology in the very while we are tackling with newer technology. Now, actually

[00:11:32] Michael Hawk: starting to emerge to help with.

[00:11:36] Dr. Brian Brown: People have proposed that a small chunk of the organisms DNA can be used like a barcode and they call it DNA bar coding for identifying specimens. So if you get this small chunk, you can really quickly match it to one species or one very close group of species in a way that doesn’t require hours of microscope time.

[00:12:01] Like for me to identify one of my little flies when I say little there. They range from the world’s smallest fly, which I described many years ago. Most of ’em around one or two mil millimeters long. So too, to identify one of these flies, you have to look at it under a microscope.

[00:12:15] Of course, you have to look at characters of the wings, bristles on the legs, bristles on the head and the male genitalia. So I like to tell people, I spend a lot of my time manipulating tiny male genitalia for a joke, but it’s true. And so you take those little male genitalia and you clear them and you examine them and then you have to run ’em through those keys.

[00:12:40] It can take half an hour to identify one specimen. And obviously that’s not going to cut it in a world where there’s tens of thousands of species of phorids and other organisms and where our traps are bringing in thousands of specimens a day. So we can either do it the way we’ve been doing it for the last 250 years, just skirting the outside of the world’s diversity.

[00:13:07] Or we can dive in with sort of industrial level by a diversity studies where we go out and collect a whole bunch of stuff, put it in individual containers, they’re called 96, well plates extract DNA. And bioinformatically, that is by getting sequences of those chunks of DNA, the barcodes for all the specimens, using that information to cluster the specimens together.

[00:13:35] So you know, that everything that has this barcode is this thing and everything that has that barcode is something else. And if you get a barcode you haven’t seen before, maybe it’s something new. so you can cut out a lot of work by doing that way. That’s not to say there’s no work and there’s no expense involved, but it’s a different kind of work.

[00:13:56] Instead of having me at my salary, looking at every fly for half an hour or 10 minutes or whatever, you get technicians running through huge amounts of trap samples and Barco them and using bioinformatics to separate them out that way. It’s the only way to handle this kind of diversity, but it’s contentious.

[00:14:20] Yeah.

[00:14:20] Michael Hawk: So I think DNA barcode could be an entire episode in and of itself there. So I’ll try to limit my questions on it. So what it sounds to me like, like, I think about all of the genetic diversity in a given species it sounds like what this process does, is it abstracts away some of the variants that you would see the barcodes, an abstraction of the species, essentially.

[00:14:43] So the small variants that might occur from individual to individual within a population or within a species would not surface to the barcode level. Is that, am I guessing correctly here?

[00:14:55] Dr. Brian Brown: Yeah. It’s just like any other character, really. I When we look at, I know birds and we see that one is blue and one is orange. We’re making a statement when we describe that species that all other members of that species are blue and all others of that. Species are orange. It’s a probability statement, right?

[00:15:15] So there is variation , you have to take that into account bar coding does exactly what you said. It takes that aspect of its genetic code and uses it to try and shortcut an identification. How much , these species are correspond to real species. We don’t really know. We don’t really know with morphological or , visible character based identifications either because really to understand how a species works.

[00:15:46] We have to know that it’s a closed breeding group, interbreeding group of organisms that doesn’t interbreed with other groups. How many small insects is that been tested on? Not many. So we use characters of the genitalia, the wing venation, and so on as proxies for reproductive isolation, things that tend to look alike, tend to be species.

[00:16:09] So we’re doing the same thing with the DNA barcodes,

[00:16:12] Michael Hawk: Another basic question you talked about in the, I guess not so old days in the relatively recent days, when you had to look at these species under microscope and particularly the male genitalia, does that mean that females you were not able to identify to species or

[00:16:31] Dr. Brian Brown: many groups, that’s for many groups that’s true or vice versa. There’s some groups like parasitoids, the females are much more distinctive than the males

[00:16:40] Michael Hawk: Okay.

[00:16:41] Dr. Brian Brown: app.

[00:16:42] Michael Hawk: Yeah. So that’s another benefit then.

[00:16:44] Dr. Brian Brown: Exactly. Not only males and females, but immature stages too.

[00:16:48] Michael Hawk: Very cool. And yeah, one, one of the other mental models I used to just try to wrap my head around the diversity that exists in the world of arthropods and insects birds, as a comparison, which people are so familiar with, roughly there have been 10,000 species of birds. That’s the number of people like to banter about.

[00:17:09] And. With DNA analysis with genetic analysis. There’s a lot of people that think that, that number’s gonna double over the next decade. So even just looking at birds, which are so well studied, and it’s a, back to your point of, there’s probably more people studying birds than there are bird species.

[00:17:26] And even then it, the outlook is doubling of number of species. So in the world of insects, it just, it’s gotta be so many orders of magnitude more.

[00:17:35] Dr. Brian Brown: So if you take the birds and even if you generously double the number of species to 20,000, that’s still nothing compared to. Flies. For instance, we have 160,000 described species of flies. And that number is certainly gonna more than double. That may be 10% of what’s really out

[00:17:55] Michael Hawk: , it’s crazy to think about. And each of those have their own. Niche lifestyle or their own dependencies in this broader food web. It just it’s phenomenal.

[00:18:05] Dr. Brian Brown: And some of them are incredibly specialized. There was a phorid fly that was described a few years ago that was feeding on fungi inside the bodies of dead stink bugs. So this fungus was growing inside the body of carcasses of other insects. This phorid fly was specialized on that. There are species that are predators or scavengers, I should say, on dead snails.

[00:18:29] So you can go out and crunch a snail and the flies will come in, but only one kind of snail. There are ant parasites that I work on ant decapitating flies go after them only after one host. So they’re incredibly finely partitioned out in the environment. It would just be the most beautiful tapestry of art to be able to put together a real entire food web for a rainforest.

[00:18:56] For instance, just the number of interactions would be mind. Boggling

[00:19:01] Michael Hawk: love to get into some of the, these detailed life histories, like the ant decapitating for fly. And before we get there, you started to hit on some of the scope of phoridae. That you have a lot of them in the tropics. It where else do they live? And tell me a little bit more about the diversity that you see just within that.

[00:19:21] Dr. Brian Brown: Phorid flies are found worldwide. they’ve even been collected on Antarctica, but inside the houses that the scientists are using there, they’re um, most diverse in the center of the world and the tropics in the rainforest, but they occur all the way on north to basically the end of vegetation and beyond I once went on a collecting trip to the Arctic and I was told by many people, oh, don’t bother going.

[00:19:46] There’s no phorids, but of course there were phorids everywhere. And even though we couldn’t put up our traps, cuz there were no trees there. We used canoe paddles to stake up our insect traps, which are called malaise traps. And they look like tents with that collecting bottle on the top and using these malaise traps, we’ve sampled many places in the world and it’s not unusual.

[00:20:07] Like I said in the tropics to get up to around a thousand species. At a single site and using this information, one of my colleagues, Emily Hartop and Rudolph Meyer predicted that there were many times more species in Africa than what we expect. They predicted a hundred thousand species of phorids in Africa alone.

[00:20:30] That’s pretty amazing, but they could only do it with DNA barcodes because who’s gonna sit down and figure out all those little species.

[00:20:37] Michael Hawk: Have you found phorids in the gardens by the.

[00:20:41] Dr. Brian Brown: Yes, we have, we found close to 200 species in LA now in . Um, And we found 50 new species to science that no one had ever seen before or who had no one had ever described before. I should. Because we looked in such detail and this was not using uh, DNA barcodes. This was using the old fashioned method looking at genitalia.

[00:21:04] And it was pretty surprising to many people that even here in the city of LA, where, we have Cal tech and all these other great institutions like Los Angeles county museum, where I work UCLA. And so on that huge amount of the city’s biodiversity is still unknown because it’s small, once you get down below four millimeters, you’re at the frontier, I can go anywhere in the world and find new species of, phorid flies.

[00:21:33] I’ve met that challenge already. One

[00:21:36] Michael Hawk: You hit a couple fascinating specialization stories with the snail and the ant decapitating flies are there generalists in this family as well?

[00:21:45] Dr. Brian Brown: for it is one of the most proliferous that’s widespread or generalist feeding of any fly it’s called Megaselia scalaris. It’s been reared from just about any kind of decomposing organic material, including paint and boot Polish. They’re found in every insect zoo around the world anywhere where people keep animals in captivity, Megaselia scalaris is going to be there.

[00:22:12] That has given phorids the reputation among general entomologists as being all scavengers. If you look in a textbook, it says phoridae family of , scavenging, diptera, somewhere parasites with of ants. And it’s really the other way around what we know so far is that phorids are one of the largest families of parasitoids and a few misbehaviors are general scavengers that cause problems for people.

[00:22:41] Michael Hawk: If, say like I’m in San Jose, California I have a small yard with some native plants, some ornamental plants. Would I be able to go outside or maybe even inside and find phorid flies? Are they just too small? The ones around here?

[00:22:56] What would your observation be about my ability as an amateur to go find some of these.

[00:23:02] Dr. Brian Brown: You could find them. You have to know what they look like. Of course they have a very particular way of running. It’s a jittery stop, go running pattern. So if you look at your windows, when the light’s coming through, there’s often flies there, especially if you leave your front and back door open, that turns your house into a big malaise trap and you can uh, get insects coming in.

[00:23:23] You can look for ’em at your windows. But probably the easiest way to attract them would be to get some decomposing meat, like some old chicken or shrimp or something, go into your backyard and bury it about, I don’t know, six inches deep. And within a couple of days, you’ll see the flies coming and zigzagging running around the ground.

[00:23:45] On top of it, phorids do a great job with carrion that’s rotting, meat, or bodies. That’s out of sight. They get outcompeted by the big blow flies, like blue bottle flies. And so I’m, those things are monsters. They come in, they have this blast eggs all over everything, and they’re huge. Larva start chomping away for little phorids.

[00:24:09] Can’t compete with that, but once you bury it, then the blow flies can’t get to it. And the phorids go down there. There’s one phorid called the coffin fly. that is quite famous because it’s found in large numbers on buried bodies. So you’ll see them in your backyard where you’ve buried some of the chicken or whatever you put out there.

[00:24:30] And three or four other species have come as well. So yeah, if you wanted to see phorids, you definitely could. They’re all around, but there’s also so many that we don’t know what they do. Like the majority of them, we have no idea. Last month I was up in San Luis Obispo county, which is in the central coast here in California. So looking at these beetles that were feeding on Willow leaves on a trail in Mon Montana de Oro state park.

[00:24:59] And all of a sudden I saw there was some pupae of these beetles. Pupae are like chrysalis’s of butterflies. On this one, pupa whether it’s one of my flies, I said, what the heck she was there laying eggs on it. Turns out there’s one, a species of this fly that is a parasite of beetles.

[00:25:16] I didn’t even know about her. just trying to find the the lifestyles of these little flies is like the smallest needles and the biggest haystack imaginable. Sometimes it’s pure luck. Sometimes it’s systematic searching when, a theme to work on like ant parasites and fireflies.

[00:25:36] You mentioned them earlier. I did a whole study on Firefly parasites but they’re there.

[00:25:42] Michael Hawk: And I’ve talked about parasitoids in the past with different entomologists. But just to level set everybody, can you remind me what a parasitoid is? What would qualify as a parasitoid and

[00:25:54] Dr. Brian Brown: Sure in insects, there’s three levels of Carvery or meat eating there’s parasites, which are insects that feed in the body of other animals, but don’t kill them. There’s predators that feed on many hosts and there’s, parasitoids that feed on and kill a single.

[00:26:15] Michael Hawk: the famous ant decapitating for it is actually a parasitoid.

[00:26:22] Dr. Brian Brown: Yeah, all ant decapitating flies are parasitoids. There’s probably, there’s about 300 species of ant capitating flies. Most of which I’ve described. And there are hundreds more, maybe thousands more that exist mostly in the new world, tropics, but they occur all the way up to treeline here in north America as well.

[00:26:44] Michael Hawk: what’s going on there with why decapitating,

[00:26:48] Dr. Brian Brown: Yeah, this was discovered by an old geezer in Washington, DC back in the turn of the last century was sitting on his porch in Virginia. And he was watching some ants crawl around and suddenly he saw one of them, the head fell off. He thought that was weird. And he picked up the head cuz he was an entomologist and he put it in a container.

[00:27:11] And a few days later a fly came out. So obviously it was parasitizing these ants. So that was the first ant decapitating fly the flies, lay their eggs inside the bodies of ants flies have this very sharp tip of their abdomen. Call them ovipositor that they can use to get between the sclerites on the ants body.

[00:27:34] When I say a sclerite. We know insects are hard bodied, right? They’re skeletons on the outside. But if it was all just molded out of one piece, they wouldn’t be able to move. So they have joints and it’s plates come together and they’re held together by membrane. So this is a chink in the armor of the host.

[00:27:55] We call it an insect. That’s the victim of parasites, a host. So the flies can come along and lay their eggs through the mandibular suture. That’s where the mouth parts articulate. The antenna suture, the occipital foramen. That’s where the head is held onto the thorax between the abdominal segments or between the thoracic segments and flies may lay their eggs anywhere in the body of the hosts.

[00:28:23] Certain flies will only lay their eggs in one place. They’ll only lay it in the head only late in the abdomen. Only lay it in the thorax, but often even if they lay it in the abdomen, the larva migrates internally through the ants body, to the head where it does its feeding. There are also certain phorid flies that are specialized to develop in the legs of their hosts, just feeding in the legs.

[00:28:50] So theoretically, you could get nine different forward flies from a single ant, get one in the head. One in the thorax, one in the abdomen and six in the legs.

[00:29:02] Michael Hawk: given the billions of ants on the earth that maybe that’s actually happened.

[00:29:08] Dr. Brian Brown: I wouldn’t put it past phorids to do something like that.

[00:29:12] Michael Hawk: these species that are parasitoids of ants. Are they selective about which T species.

[00:29:17] Dr. Brian Brown: For the most part, they’re very selective. And this is important because some of these flies have been , used to attempt biological control of imported pest ants, like fire ants in the Southeast of the United States. So you have to be very careful that you don’t bring in something that will go onto the native ants and cause problems.

[00:29:39] Usually it’s not an issue. There have been some introductions of phorid flies without due caution. I think so far it hasn’t caused any problems, but the argument is that the fire answer causing much more havoc on the native, ant fauna than the parasitoid would. I don’t really agree with that.

[00:30:00] I don’t think it’s necessary to bring in questionable biological control agents, but it has been done.

[00:30:07] Michael Hawk: Yeah, it’s it doesn’t take too much of a leap of thought to see that going wrong. in some respect,

[00:30:14] Dr. Brian Brown: There’s so much introduction and upheaval of insect species in urban areas, especially, but around the world where people are through commerce are bringing in goods from all over the place here in Southern California. For instance, we had a spider survey and we had uh, healthy population of black widow spiders.

[00:30:35] In the. About 10 or 15 years ago, we noticed that brown widows of species from Africa were starting to show up here and within a year or two, they just about completely eliminated black widows from the urban areas of Los Angeles. That was interesting. And then like in the last year or so, the noble widow has come in and just about wiped out all the brown widows, same thing with the argentine ants.

[00:31:01] There are a big influx of them in the, what was it? The end of the uh, 18 hundreds. They were brought in probably with nursery stock to north America. And they wipe out all the native ants wherever they are. So that was a big problem. Now in my backyard, at least they’re being completely eliminated by another introduced ant, .

[00:31:21] So who knows what’s gonna happen next? That’s a giant experiment that we’re conducting without even noticing really.

[00:31:28] Michael Hawk: Yeah, in, in my yard, I’ll have to look and see if brown widows have made it to the bay area, but I have a healthy population of black widows and the noble false widows coexisting . Maybe without the introduction of the brown widows to kick out the black widows those two perhaps are able to coexist interesting to think about.

[00:31:49] Dr. Brian Brown: That’s the best case scenario, right? The worst case scenario is that something like the Brachymyrmex patagonicus, the ants that wiped out the Argentine ants here allowed the imported fire ants, which are also here, but which are suppressed by the Argentine, a allows those things to get going.

[00:32:06] Cuz at least with argentine, ants they don’t sting,

[00:32:09] Michael Hawk: Yes.

[00:32:10] I’ve seen some video clips? I can’t remember if it was through the national history museum website about some active research going on in the tropics where you are looking for forward flies and probably other things too. Can you tell me.

[00:32:24] What you’re working on in terms of understanding the diversity in the Tropic.

[00:32:28] Dr. Brian Brown: tropical biodiversity is really astounding. It’s so much higher than anywhere like here in California. And it’s just inspiring and beautiful to me, even though it’s also hot and. Full of mosquitoes and other petty inconveniences. It’s just the place to be doing research. So a couple of years ago, just before the COVID pandemic, we went down to work on a tower in the rainforest.

[00:32:57] This is a atmospheric study tower that goes right up to the top of the trees. And one of my colleagues down there, Jose Raphael had the fantastic, brilliant idea to put malaise traps, those tents with the bottles on them at different levels in the forest. And when I looked at the samples from this material, I thought, oh my God, it’s like, they’ve discovered another continent things I’d never seen before.

[00:33:24] Things that were super rare or new. So I said, we’ve gotta go down there and do some more work. So we went down and made some more collections and started identifying the material that had been collected and found that in the flies, there are subdivisions of the forest that nobody had recognized before.

[00:33:45] People have looked in general at the subdivisions of the forest, like the forest floor versus the eight meters above, just above our heads and right up at the top of the canopy and different groups of flies families were using this space differently. Unbeknownst to us, we knew that based on the general studies that about 60% of the species are only found above the forest floor.

[00:34:12] If you’re a ground level bound scientist, you’re only seeing, you’re seeing less than half of what’s actually there. Once you get above that, you start seeing all kinds of things. And there are some families that are 90% above the forest floor. And so it’s really amazing how this forest canopy or the levels in the forest is being subdivided by these animals in ways that we don’t understand yet.

[00:34:38] And there are practical problems with this, not understanding it. So for instance, when someone says, oh, we can do selective logging. That is go in, just take out the big trees. The forest is still there and you’re not causing much damage. Maybe you are. And maybe you aren’t, if you’re destroying the stratification of the forest by doing this.

[00:35:01] Although

[00:35:01] Michael Hawk: I think that’s really interesting because what that starts to hit on and I, you were alluding to this and stating this actually directly is all of them. The other relationships that trickle down from this stratification of the insects, there’s there’s probably predators, birds, other things that are dependent on the stratification as well.

[00:35:19] And again a sensitive system that we don’t know much about. Oh,

[00:35:22] Dr. Brian Brown: I am sensitive to the insects as food argument, why we should save biodiversity? People ask me what good are insects. And one of the uh, arguments that’s often trotted out is. They’re food for other animals or food for birds as if birds are more important than insects, but we all know that insects fundamentally are more important to ecosystems than any vertebrates.

[00:35:47] Michael Hawk: absolutely. Yeah. tell me why. I don’t want to answer that or leave it up to the listener, but tell me why.

[00:35:53] Dr. Brian Brown: They just handle things at the different level and more basal level in the uh, in the food pyramid. They’re important for decomposing. They’re important for pollinating. They’re important for doing all kinds of things without which life would be impossible. Birds are the, I know gilded trimming on the top of the biodiversity cake, I guess.

[00:36:15] Michael Hawk: yeah, without the insects, we wouldn’t have healthy soils. We wouldn’t have pollinated plants. We wouldn’t be transferring all these nutrients up the chain. everything would break down.

[00:36:26] Dr. Brian Brown: Yeah. And those sorts of services are not valued, particularly , if they were they’d be in the billions or trillions of dollars annually, but we take ’em for granted.

[00:36:37] Michael Hawk: So I have a listener question that I wanted to ask, and you talked about how the tropics are the place to be for this research, because it just so phenomenally diverse and then some of the downsides like the mosquitoes. So here’s the question. And they actually started with, I’m guessing that you get this a lot, but bot flies, as I understand it, bot flies, lay their eggs on mosquitoes and mosquitoes deliver the egg to their host.

[00:36:59] Is this true? And is it only mosquitoes doing this dirty work or are there other I’m reading the end of this, are there other delivery mechanisms? And will the bot fly larva be able to exploit any host? The mosquito happens to choose.

[00:37:13] Dr. Brian Brown: last part? I don’t think so because bot flies are specialized on certain hosts and it may be the uh, the mosquitoes themselves that are specialized on the hosts. I’m not sure, but yeah, bot flies will lay their eggs on mosquitoes. They’ll also lay their eggs on stable flies, which are another group of biting flies and they.

[00:37:34] These biting flies actually deliver the eggs. There’s a great David Attenborough sequence in one of their life on, I can’t remember. There’s so many of those series where it shows the bot flies grabbing one of these biting flies and gluing the eggs all over it. So yeah, that’s how it works. And it’s a painful process.

[00:37:55] Having a bot fly larva in you, cuz bot fly larva. They’re not feeding on your healthy tissue, but fly larva have little spikes all around their body. And what they do is they twist and turn inside under your skin. And that causes lacerations. It causes tissue to be damaged and then bacteria get in there and the bot fly larva actually filter the bacteria.

[00:38:19] That’s what they feed on. They’re not feeding on your skin. So they keep the wound relatively clean. And I say relatively, I just got tired of a dribble of POS and blood coming out of my back, but they’re not like some of the dangerous flies, like screw worms, where they actually attack living tissue and they feed on that directly and they can cause real damage.

[00:38:42] Bot fly larva or generally as long as they’re not in an eye or something inconvenient and somewhat painful, but not dangerous and gross

[00:38:52] Michael Hawk: I just had a friend come back from a tour in Ecuador and that was one of my first questions. You did you get a bot fly? And she said I don’t know yet. so I, how long does it take , before it’s evident?

[00:39:05] Dr. Brian Brown: few days.

[00:39:06] Yeah. It’ll be like a mosquito bite that doesn’t really heal. And then you can start seeing the larva. Sticking, its breathing apparatus outside your,

[00:39:15] Michael Hawk: fun. I don’t wanna over blow that I think people have too much fear of insects as it is, , it, this isn’t something that happens every time you go to the tropics, this is still a fairly rare.

[00:39:26] Dr. Brian Brown: has happened to me once and I’ve been many times to the traffics. You can avoid those things, sensible precautions. It’s just that scientists are not always , sensibly, pre cautious when it comes to the tropical forest. Because number one, if you’re studying flies, you don’t wanna wear a bunch of clothing.

[00:39:44] That’s been impregnated with fly killing chemicals. And number two, when you’re out there working, you lose track of time. Of your surroundings, everything, because it’s so engrossing to sit and watch these things, doing their activities. When I got my, bot flies, it was the time that we discovered the new type of ant decapitation in the phorids.

[00:40:07] we had known for a hundred years that phorids females would go, like I said before, fly around and lay an egg inside the host larva would feed and through its feeding would eventually cause the ants head to fall off. That’s keeping it a little bit simplified, but that’s basically what happened. We found another type of ant decapitation in phorids because God knows one isn’t enough.

[00:40:33] And that was

[00:40:34] Michael Hawk: And

[00:40:34] Dr. Brian Brown: a species in Brazil where the flies would be attracted to adult ants that were injured and injured are super common In the rainforest, we’ve found that empirically just by looking, but also by studying flies that are specialized on injured ants, they just be must be super, super common.

[00:40:57] So these flies, you put out an injured an if this one species, the flies come, the females, they use their mouth parts to cut the ants head off and they drag it away with their prehensile four legs. It’s really amazing. They just grab the ants, head and tug on it until it falls off. And then they carry the head away and lay their egg on it.

[00:41:16] So that’s the second type of an decapitation in this family.

[00:41:20] Michael Hawk: Dr. Brown, thank you for all the time you spent today being cognizant of your time and how much we’ve allotted. Let’s move on to some wrap up questions. What have you found to be most effective in helping people move up a rung

[00:41:34] Dr. Brian Brown: me, it’s, I’ve found my years at the museum. It’s really important to get out in the field with people. You can’t explain abstract concepts anywhere, nearly as easily as you can. Just showing them things. So when I take people out in the museum garden, I take them to a flower and I say, see that’s a flower fly flying in there and see this is a bee bees, fly back and forth as they’re going towards their flowers.

[00:41:59] And I get people

[00:42:00] Michael Hawk: awareness?

[00:42:01] Dr. Brian Brown: phoning me weeks later saying, you never guess I was sitting in traffic, watching the insects on this median. And I saw a flower fly landing right on the flowers beside me, right in Santa Monica. They get their search image and they get interested until they actually see those things biodiversity.

[00:42:19] Like other things are effectively invisible to them. Until you show somebody something until they can put some kind of experience together with it. They’re invisible. This happened to me in Costa Rica. If I can tell a quick story, the first time I went to Costa Rica I did my research for a couple of weeks at a research station in the rainforest.

[00:42:40] And then I came home and somebody asked me, did you see any orchids down there? I said, no, I didn’t see any orchids. Then I started getting interested in orchids. I started growing them and learning about their different structures and what they look like. And the next time I went down to the tropics to the very same place I saw orchids everywhere.

[00:42:59] So yes, my eyes reg, my retinas registered those photons coming off those orchid leaves. But until you get a, some kind of knowledge or some kind of experience with them, they’re effectively invisible to you. It’s a green wall. So I think that we need to get people, especially kids out, into nature and show them things, get them interested in them and not leave them to just experiencing nature from TV shows.

[00:43:29] I

[00:43:30] Michael Hawk: you’re showing people. Insects in particular. And I’m thinking of flower flies. A lot of the flower flies are quite small. Do you have additional visual aids? Like here it is, but it’s so small. Here’s a blown up picture. Look at how beautiful it is. Or do you just let them experience the raw nature.

[00:43:45] Very

[00:43:45] Dr. Brian Brown: don’t use any aids you can use magnifiers that go onto binoculars that make them focus a lot more closely. Some people do that, or you can get reading glasses, the three power ones, even if you don’t need them, you put them on. And looking at flowers becomes a whole different world, but really things aren’t that small.

[00:44:05] Even the tiny one millimeter long phorid flies that are parasites of fire ants we work on without any kind of. Visual aids. It’s more learning how the animals move, how they look, what color they are and so on. You can see quite a bit.

[00:44:21] Michael Hawk: cool. That’s a great tip with the reading glasses. I mentioned that to somebody, myself recently and I don’t do it enough personally, but I’ve done it in my backyard. That’s for sure. And do you have any upcoming projects or activities? Either personally or through the museum that you’d like to high.

[00:44:37] Dr. Brian Brown: I do, but I don’t know if they’re highlightable. I plan to continue working in the tropics, making new discoveries. I like to try to find unknown life histories. Things that will be captivating to the general public, because if there was one thing I could point to as the best result from my work, then that would be saving tropical rainforest.

[00:45:03] That is my ultimate goal yet people to care, or even to think about tropical rainforest when they wouldn’t, again, not to look at a chunk of land as so many board, feet of timber or so many cattle grazing units, but as an interconnected community that needs to be protected. And uh, I think it’s time for Westerners with all their money to put their money where their mouth is and to support conservation organizations in the countries where these forests occur to a much greater level than they do now.

[00:45:39] Michael Hawk: Do you have any organizations that you would like people to support that you want to call out?

[00:45:44] Dr. Brian Brown: Rainforest trust nature Conservancy. And there are tons of smaller ones where you can make a much bigger difference as an individual, because their needs and their budgets are smaller, , but I think also the work being done by Dan Jansen in Costa Rica is really inspiring going down there, , making his career, the study and preservation of the habitat in which he works, which is a tropical dry forest in Guana Costa Rica.

[00:46:13] That must be just gut wrenching for him to see the loss of biodiversity over the last couple of decades. And largely not due to anything that’s going on there in Costa Rica in particular. I think that a lot of this global insect loss is due to climate change mean insects are highly oriented towards timing of events in the forest.

[00:46:38] So if they’re waiting for the rain to come, they hatch out and there’s no rain, no new vegetation for the caterpillars to feed on, they all die. Then that’s it for that generation. And this is happening all over the place. You have to uh, go around the world and go to rainforest and everybody will tell you, oh the timing is off in the last decade.

[00:47:00] It doesn’t work anymore. The rains are two months later or come in the wrong time. And I think this is the biggest problem that we face.

[00:47:11] Michael Hawk: On a personal level. You telling me that makes me realize that so much of what I’ve attributed insect loss to has been pesticide use. And

[00:47:20] you saying that really really brings home the point of climate change being so pervasive. I hadn’t thought about that with respect to insects but yeah, it certainly makes sense. Absolutely.

[00:47:34] Dr. Brian Brown: Yeah, it didn’t come home to me until I went to the middle of the Amazon and everybody told me the same thing was happening there. And they’re not using pesticides per se in this area. They’re not, they’re surrounded by the biggest. Forests left in the world. And yet they’re still having these same problems.

[00:47:53] It’s clear to me that it’s a global problem, not a local one and pesticides don’t help.

[00:48:00] Michael Hawk: well Thank you for bringing that to light. I think hopefully others are drawing those same connections that I just drew. And if people want to continue to follow you, follow your work social media or through the museum, where can they go? Yeah. It

[00:48:14] Dr. Brian Brown: That’s a good question. I’m not a high profile sort of person, but you can keep up with me at the museum, the natural history museum, nhm.org. I have a blog. That’s got a lot of information about flies called fly obsession dot. and if you’re really interested in phorid flies, not many people will be this interested, but phorid.net, P H O R I D.

[00:48:38] Dot net is my resources for scientists. Let me say, there’s only like probably there’s only three scientists in the world who are currently employed to work on forward flies, even though they’re probably a larger group than all the birds, mammals, reptiles, amphibians, and fish put together. Sure

[00:48:58] Michael Hawk: mind blowing and thank you for doing that work. And surfacing, everything that you have through that work is just amazing to think about. And speaking of thanks. Thank you. I really appreciate you. And the time you’ve spent today and the work that you do, I hope that you’ve had a good time chatting today.

[00:49:15] Dr. Brian Brown: I could go on and on, but you’ve got time constraints too.

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