How I Discovered 30 New Species of Flies in Los Angeles

By Emily Hartop

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Aaron Pomerantz of Next Gen Scientist on BioSCAN and Los Angeles’s 30 Newest Species

When I came to work at the Natural History Museum of Los Angeles County, I had no idea exactly what was in store for me. The NHM had recently initiated a massive study to search for biodiversity, or the variety of life forms in a particular area. This study wasn’t taking place in some lush tropical jungle, though; in fact, far from it. This fabulous study was (and is) taking place in the backyards of Los Angeles. I got hired to be part of the entomological team for this urban project called BioSCAN (Biodiversity Science: City and Nature) and before I knew it, I was describing 30 new species of flies collected right here in the City of Angels.

Before I explain how this all happened, let’s pause and say that again: 30 new species of flies were described from urban Los Angeles in 2015. Let’s expand: these flies were caught in three months of sampling and are all in the same genus. What does this mean for us? It means that even in the very areas where we live and work, our biodiversity is critically understudied. It means that in your own backyard, or community park, live species that we do not even know exist. It means that all of those invisible ecosystem processes that occur all around us are being conducted, in part, by creatures we know nothing of. It means BioSCAN is off to a good start, but we have a lot of work to do.

Beginnings

My boss, NHM Curator of Entomology Dr. Brian Brown, has spent years working on an amazing group of flies called phorids. When I started in January 2014, I knew next to nothing about phorids; I knew they were small flies that did some cool things (like decapitating ants and killing bees and eating cadavers in coffins) and that was about it. When I came in to volunteer my time prior to my official start date, Brian sat me down with some samples from Costa Rican rice paddies and asked me to pull out all the phorids for further study. I only vaguely knew what a phorid even looked like, so I had a steep learning curve that first day. Soon, though, I could recognize a phorid as easily as picking out an orange in a bunch of apples.

After I got a feel for phorids at the family level, I had to learn the Los Angeles species so that I could identify them and we could start tallying them up for our project. Brian taught me some of the genera in the family and their characteristics. Then he showed me a species called Megaselia agarici. This species has a prominent, pale protrusion on its genitalia (and speaking of genitalia: I’m going to say 90% of our identification work focuses on these for flies, we are obsessed with fly genitalia…), making it easy to pick out at the species level. Great! With my notebook in hand, I eagerly asked Brian, “So, I can pick out this species, but how do I know this group on the generic level, what is a Megaselia?” Brian’s response should have dissuaded me from this group: “Megaselia is a giant genus, about half of the phorid family. Eliminate the other genera as possibilities and if it’s not something else, it’s likely Megaselia.” A sane person would have left it alone. A sane person would have quietly learned the few Megaselia species that are well known and easy to recognize and quietly set the rest aside for someone else to deal with. But not me. I became intrigued.

Getting to work (and to tea)

The flies!  Photography by Kelsey Bailey.

The flies! Photography by Kelsey Bailey.

I started to see the same species over and over, I started to notice small differences between the flies when I would sort samples. I started to make little sketches and write notes. Gradually, I started giving these flies funny names: this one’s genitalia look like bunny ears, I’ll name it “Bunny”, this one has setae (socketed hairs or bristles) that remind me of a 1980s troll doll, I’ll name it “Troll”. I even had a species nicknamed “Hokusai” after the famous painter because its extruded genitalia looked just like details found in The Great Wave off Kanagawa. My colleague, Lisa Gonzalez, contributed by naming one I showed her “Sharkfin” because of its uniquely shaped midfemur. Slowly, the list of “species” I was able to separate grew. I started reading literature on the genus, and then I started working with the keys (identification tools) for the group. To my surprise, I couldn’t get most of my nicknamed flies to come out in the keys we had for the North American fauna. These keys were written back in the 1960s (the last time someone seriously took a look at the genus on this continent), and just a smattering of publications on the group in this region have been published since. I couldn’t really believe it, but it didn’t seem that most of my flies had been studied before.

Many of the publications I had as references were written by the current world expert on the genus Megaselia, Dr. Henry Disney, who is retired (but still very active in research) from Cambridge University in England. Like my boss in L.A., Henry Disney works exclusively on phorids. And although Brian has kept very busy with other genera, Henry Disney has studied Megaselia for decades. I joked with Brian that I had to go “have tea with Disney” to learn the secrets of Megaselia. Then I realized: I wasn’t joking. No matter how many papers I read or drawings and photographs I looked at, I needed help from someone who knew these flies. A few months later, I was in Cambridge, studying with the master.

I spent weeks in England side-by-side with Henry Disney identifying flies (and yes, we had tea together everyday, twice a day!). To determine if a Megaselia is new to science, you take it through every key for the genus ever written in the world. Megaselia have a way of getting transported across oceans and continents, so you never know when a species that turns up in California might be one originally described elsewhere. These keys are numerous, and in a handful of languages. Luckily for me, Dr. Disney had the whole process down to a science and we worked through all of the flies I brought with me. I left with a lot of work to do back home, but the potential to have several dozen new species!

The business of describing species

Once back home in California, I used the Natural History Museum’s collection of phorids to compare my flies with potential matches from the literature. This is done by looking at holotypes, which are “model specimens” of a species designated by an author when a species is described. After all was said and done, I ended up with 30 new species of flies in this one genus, after just three months of sampling. But my work was far from over.

Next came pictures of each fly. A whole body photograph, a wing photograph, and detail photographs (I was lucky enough to have an awesome intern, Kelsey Bailey, to do these for me). The flies had to be carefully dissected (using fine pins under a microscope to carefully remove wings, legs, etc.) for detail photos. Many specimens were mounted on glass slides to be examined further. Using these slides, I carefully sketched the genitalia of each new species, and then drew clear and accurate drawings digitally from my scanned sketches. Then Brian looked over my drawings and, in the kindest way possible, told me that I had drawn certain features (like the aforementioned setae) completely wrong. So I learned how to draw all the features of my flies accurately and realistically, and then I learned some more. I can confidently say that at this point I’m a competent (perhaps even slightly accomplished) fly genitalia artist, and you can see my handiwork for these new species below.

The Genitalia!  Drawn by Emily Hartop.

The Genitalia! Drawn by Emily Hartop.

After all the sweat and tears of genitalia illustration, I designated holotypes, and secondary “model specimens”, called paratypes. I carefully detailed each species morphology, complete with dozen of measurements down to fractions of millimeters that took hours upon hours counting little scale bars through a microscope. I described where each fly keyed in the literature and how it failed to match any similar described species. In some cases this is very difficult, and in others, problems with the original specimens used for a description leave unanswered questions. The process takes a long time and it’s not easy. And then there was the issue of naming these flies (my silly nicknames, alas, weren’t fit for scientific publication). I had 30 new species and, conveniently, BioSCAN has 30 sites. This meant each of our fabulous site hosts got a fly named after them. Amazingly, Lisa was able to use our data to match each new species to a site where it had been found, and name each fly after a person or family that actually had that fly in their backyard. Since one of the 30 sites is the Nature Garden at NHM, the 30th species we named in honor of the Seaver family, whose foundation helps to fund BioSCAN.

Aaron Pomerantz of Next Gen Scientist on BioSCAN and Los Angeles’s 30 Newest Species Part 2: BioSCAN in the Field

On from here

For months on end I spent my days buried in fly genitalia. I did, I became a crazy fly lady. But just a year after I started getting to know and love these flies, I’ve helped to describe 30 new species right from the heart of my city… but I’m not stopping there. Not only are there cities around the world with Megaselia just waiting to be discovered, but in the jungles of the tropics the numbers of new species go from dozens to hundreds. Beyond that, we have to figure out what all these incredible new flies are doing. If other phorids decapitate ants and eat human remains, what could these 30 new species be up to here in Los Angeles? I have a lot of work to do: I’m coming for you, Megaselia!

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23 thoughts on “How I Discovered 30 New Species of Flies in Los Angeles

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