Urban phorid flies in Los Angeles, California, USA

Last week Emily Hartop and I published a new paper on the phorid fly fauna of Los Angeles, in the journal Urban Ecosytems (get the full text here). This is the culmination of years of work by all of the BioSCAN team, in getting the project up and running, sorting and identifying 40,000+ flies (mostly Megaselia, mostly the work of Emily), and looking for patterns in the community.

Lisa Gonzalez of the BioSCAN project and Joe Hogg, one of the site hosts, in Joe's backyard.

Lisa Gonzalez of the BioSCAN project and Joe Hogg, one of the site hosts, in Joe’s backyard.

The major findings for us is that the Los Angeles urban fauna consists of about 100 species (43 of which were new to science and described by us for the first time), but individual sites (mostly backyards) had from the mid-twenties in the area just west of the museum to 83 species in Glendale, right up against the mountains.

The commonest species by far is Megaselia agarici, a fungus-feeding species possibly introduced from elsewhere. It is sometimes a pest in commercial mushroom farms, but here they are extremely common in “wild” Agaricus mushrooms that we have found in the city and brought indoors for rearing the flies. This species is so prevalent, that it was found in every one of our 30 sites (as were a few other species), and in some sites it made up over 70% of the phorids captured. Many of the other commonest species in the study were also mushroom feeders, such that at least 40% of our collected phorids have this lifestyle.

Thirty sites of the phase I BioSCAN project in Los Angeles

Thirty sites of the phase I BioSCAN project in Los Angeles

In contrast, our most diverse site had many more species that do other things, especially those that parasitize ants (including the infamous “ant-decapitating flies” I have written about elsewhere). These ant-associated species are completely absent from the downtown area, almost certainly because the introduced Argentine ants have completely eradicated the other species of ants formerly found here. It is difficult to know how much damage was caused by the introduction of “argies” here, but it was a catastrophe for phorid flies.

Many other results are in the paper, and I urge all interested fly aficionados to read it. The next step will be to associate these diversity data with variables of climate and urbanization to see if we can find some correlations that make sense. We are far from finished working on L.A. phorids! But the outstanding remaining question about this phorid community we have here is whether it is representative of other urban phorid assemblages, here in California, here in North America, and throughout the world. Are all urban sites dominated by fungivores? Do they all have a superdominant species like M. agarici (or maybe even M. agarici itself)? We just don’t have any data to know the answers yet.

Thirty of the 43 new species of phorid flies from Los Angeles

Thirty of the 43 new species of phorid flies from Los Angeles

Additionally, one of our next studies will be to look at other groups of insects (including other families of flies) to see how they are distributed in the city. I expect that there will be some major differences among groups, attributable to small-scale differences among sites. One study (Avondet et al. 2003) in Ohio, looked at, among other things, the distribution of dumpsters to help predict the diversity of Drosophlia “fruit flies” (Drosophilidae, better referred to as vinegar flies or pomace flies) in the urban landscape! Probably the diversity of plants, flowers, amount of hardscape vs yard, mulch versus grass, and so on will greatly affect the number of species at a site, but our ability to predict this is still in the infancy stage. Stay tuned for more…

Cited article:
J.L. Avondet, R.B. Blair, D.J. Berg, and M.A. Ebbert. 2003. Drosophila (Diptera: Drosophilidae) response to changes in ecological parameters across an urban gradient. Environmental Entomology 32(2): 347- 358.

The white-tailed phorid, Megaselia albicaudata

It is amazing to me that some phorid flies are found in multiple environments around the world. Less surprising are the scavengers that live mostly in human-built structures or that need scraps of our civilization to thrive. Usually, these scavengers are well-known to us, through their large numbers and occasional nuisance status. But what about the”white-tailed phorid” (I just made that name up, based on the Latin name!), an obscure but seemingly ubiquitous fly?albicaudlatsmall

There is no question that this 1.5 mm long fly is well-named: the male genitalia are a shocking white in comparison to the rest of the rather dingy brown body. It was described in 1910 from England, and is well-known from other parts of the world such as Finland, Israel, and China. It is also found in the two big fly inventories that I am part of: the Los Angeles County Natural History Museum’s urban biodiversity project called “BioSCAN” and the Costa Rican “ZADBI” project in a tropical cloud forest.

How can a species live in such disparate climates and habitats? Nobody knows, just as nobody knows what the larvae of this fly eat. I have looked at specimens from both North America and Costa Rica, and I am sure they are morphologically the same species, not two species masquerading as one doing different things in different places. It is one of thousands of Megaselia worldwide that we know nothing about, but discovering phorid lifestyles is part of our* phorid research effort. Obviously, we have a long way to go when such a widespread species remains a mystery.

*Note, when I say “our”, I mean the few people worldwide actively pursuing phorid research, including our group here at LACM, consisting of Emily Hartop, Lisa Gonzalez, and me.

Fly porn- what can we learn?

Take a look at this video of a pair of Phora I observed mating in Central California.

Apart from the humorous aspects of the “action”, including the hilarious way they kick each other to separate, there is actually some good science here.

Notice the movement of the male’s hind legs (how could you miss it!). Males of many species of Phora, and some other phorid genera, have tufts of setae (thick, hairlike processes) at the base of the hind femora. Presumably, the male uses them to contact the female during sperm transfer as a sort of courtship to persuade the female to use his sperm. Female flies often mate with multiple males, and can control to a remarkable degree whose sperm she uses. This is because the sperm from any mating is shunted to a storage organ called the spermatheca, where it is kept until needed. Females have been shown to have remarkable control over the sperm in a spermatheca, shunting unwanted or lesser quality sperm (as judged from mating stimuli received during copulation) to the back, or even expelling it. Thus, males not only have to copulate with females, but also have to convince them to use their sperm when they later lay an egg. Male signals, like the stimulation of hind femoral setae, are what convince her of the worthiness of the sperm.

Also of note is the position of the forelegs of the male, flat on top of the female’s scutum (“back”). Male Phora have thickened, flat foretarsi (the short segments at the end of the leg) that probably have specialized setae as well, but, well, nobody has really looked. It would be an interesting study for someone with spare time and access to a scanning electron micrograph.

The final aspect of the mating is the fastidious cleaning that the female subjects herself to. In insects, as in all animals, close contact with another individual always involves the possible transmission of parasites. For small flies, what we note most frequently, is the presence of mites, which can almost completely coat an unfortunate victim. This female spends a lot of time sitting on a leaf, exposed to predators (and photographers), while cleaning herself. It must be worth it, to keep away those mites!

This post is dedicated to my colleague Erica McAlister at the Natural History Museum in London, to give her something to read on a Sunday morning!



A new type of ant-decapitation in phorid flies!

Dohrn longi plateOkay, I literally have been waiting for years to write this story! Now it is published, and you can read about our amazing (at least to me) discovery.

Most phorid flies that decapitate their hosts do so by injecting an egg into the host ant; after hatching from the egg, a larvae feeds in the head, eventually causing the head to fall off, sometimes before the rest of the body stops moving.

In species of the Dohrniphora longirostrata group, however, the female flies are attracted to injured Odontomachus ants, which they decapitate themselves, and haul off the head to feed on its contents or to lay an egg. We have seen this in several countries, and on many occasions, so there is no doubt in my mind that this is a specific behavior to these flies. They are not attracted to injured ants of other types, only Odontomachus.

Here is some video of the action!

(video by Kate Lain)


No, not the operating system. I’m talking about physical windows in a building. If some doors, other windows, or even the whole side of the building are open, windows can be fantastic places to collect flies. Like most dipterists, I go right to the windows of any building I am in, to see what is there. Sometimes, people look at me as if I am crazy, but I forgive them because they just don’t realize how cool flies are yet (top to bottom, a ropalomerid, stratiomyid, and tababid).




Wendy Porras and I just got back from La Selva Biological Station in Costa Rica, where half of the dining room is wide open, while the other half has screened windows throughout. We found a lot of extremely photogenic flies, some of which I show here. We put them in a more pleasing background than screening, wrangled them to sit still, and got the shots we wanted. A little honey on the leaves helped, as some flies were apparently hungry after several hours of banging their heads against metal cables.

The Most Beautiful Fly in the World

I know that this might be controversial; after all, people generally either don’t think flies have any redeeming qualities (never mind “beauty”), or more likely for readers of this blog, have their own ideas of what constitutes a gorgeous fly.
silver strat zerenea
I submit, however, that this amazing silver male stratiomyid (soldier fly) from Costa Rica is the most beautiful fly in the world. It moves around on the underforest leaves like an animated drop of quicksilver, flashing in the tropical sun. It is not garish, like some of the gaudy calyptrates I have seen (see below), but has a pure beauty in its clean, sleek metallic cover. Just in case you find this boring, it also has a scutellum decorated with spines, like the crown of royalty.

The name of this creature is Artemita aurata (Macquart), and it was described in 1846, so it is not anything new, but it deserves “rediscovery” by lovers of biodiversity everywhere.

Don’t agree with me? Let’s hear your nominations!

OLYMPUS DIGITAL CAMERAA gaudy calliphorid from Australia: a runner-up to the world’s most beautiful fly

Forty-five seconds of fly swarming

One of my favorite museum exhibits is the round ceiling tank at the Monterey Bay aquarium, where a huge school of silver-colored fish swim in an endless circle. It is hypnotic, fascinating, and strangely calming.

Watching flies in a mating swarm can be that way too. Usually, it is a group of male flies we see, all jockeying for the best position in the air. Presumably, this allows arriving females to recognize those that are superior and choose the male in the “best” position for the one with which they will mate.

Thinking of the Monterey Bay experience, I wanted to document a fly mating swarm, and finally got the chance this summer. A group of empid flies (also known as “dance flies”) were flying in a brilliant shaft of light against a dark conifer background, perfect for my purposes. Let me know what you think of the result!

Flyobsession back online

After transferring from WordPress.com to my own site, flyobsession is back! Look forward to more stories and photos of our two-winged friends.

Pictured here is a male Adelopteromyia, a common phorid fly from the ZADBI project in Costa Rica (photo by Inna Strazhnik). The females of this genus are brachypterous (have reduced wings) and are found in army ant colonies.


ps. This image looks much better full size- click on it to see.

Diptera Blitz wrap-up

EOL micropezidOf course, our event was a tremendous success. Some highlights:

– bat-netting by Carl Dick got us streblid records, bird-netting by Kimball Garrett got some hippoboscids.

– Carlos de la Rosa (the Director of the La Selva Biological Station) joined the team, working on chironomid midge pupal exuviae

– Michael Turelli, professor of genetics at UC Davis and (at least on this trip) amateur drosophilid collector gave a stunning talk about using the intracellular bacterium Wohlbachia to eliminate dengue

– the final event, a barbeque, featured a short film about the week by LACM videographer Edgar Chamorro.

Some photos follow, including a group photo of nearly all participants. These photos help portray not only the enjoyment, but also the dedication of the team to document as many Zurqui flies as possible. The results of their efforts will appear soon on this website.

Yes, nearly all these people came to Costa Rica to study flies! (click photo for larger view)

Diptera blitz kimball
LACM ornithologist Kimball Garrett releasing a bird after checking it for hippoboscids (bird louse flies)

Manuel Art Brian
Manuel Zumbado, Brian Brown, Art Borkent: three dipterological amigos