Tag Archives: Phoridae

Phorids and other flies from the urban “wilds”

Two papers have appeared recently based on our BioSCAN (Biodiversity Science: City and Nature) project. In this project, we partner with the public by placing Malaise traps (tent-like traps with a collecting bottle on top) in backyards and gardens, obtaining the homeowner’s help and permission to sample in places that would otherwise be off limits. We call our collaborators “site hosts”.

Each of the new papers looks at fly diversity in Los Angeles in slightly different ways, and involves a team of ecologists that are helping us interpret our results.

One of the BioSCAN sites and the Sanchez family, the site hosts

The first was headed by Dr. Terry McGlynn from California State University, Dominguez Hills (the full list of authors and the full citations are given below). Terry and colleagues looked at our weather station data along with phorid diversity from the first phase of BioSCAN (the phorid diversity was described by Brown & Hartop 2015). They found a Goldilocks situation with temperature as the strongest variable: not too hot and not too cold described the optimum conditions for phorid diversity. This makes climate change a real concern, given that even phorids (tough little flies) react strongly to small changes in conditions.

The second paper, headed by former postdoc Dr. Max Adams (now at George Washington University), looked at more groups of insects (including also syrphid and tipulid flies (flower flies and crane flies) and more variables. This paper found that the amount of water that was put on the landscape was most important, and that reducing water (as in dryland gardening) increased insect diversity across habitat types as diverse as parkland and high density residential areas. This might seem counter-intuitive, since more water produces more vegetation, which should promote more insects, but it turns out that the native diversity is not impressed by this extra water. A few widespread and introduced species are the main beneficiaries of such conditions.

So, the message from these studies is that, in Los Angeles, we need to continue to work together to slow or prevent climate change, and we need to avoid having lawns and other water-extravagant landscapes. Native plantings watered by drip irrigation would be the best type of yard to promote insect diversity. Greater (native) insect diversity promotes (or is a result of) a healthier ecosystem, which favors a better standard of life for all of us living in L.A.

Publications: I am grateful to our wonderful and talented group of collaborators who have allowed us to extract meaning from the bags of insects we collect from our BioSCAN sites: Terry McGlynn, Emily Meineke (who has a new position at UC Davis- go Emily!), Christie Bahlai, Jane Li, Emily Hartop, and Max Adams. Also, I cannot thank enough our BioSCAN staff, Lisa Gonzalez and Estella Hernandez, along with the volunteers and work study students who help make the project possible. Finally, all of our 80+ site hosts who shared their properties with our traps are truly special people who care about the future of nature in our city. I hope that we can continue to bring you new insights and actionable results.

Adams, B.J., E. Li, C.A. Bahlai, E.K. Meineke, T.P. McGlynn, and  B.V. Brown. 2020. Local and landscape scale variables shape insect diversity in an urban biodiversity hotspot. Ecological Applications.

McGlynn, T. P., E. K. Meineke, C. A. Bahlai, E. Li, E. A. Hartop, B. J. Adams, and B. V. Brown. 2019. Temperature accounts for the biodiversity of a hyperdiverse group of insects in urban Los Angeles.  Proceedings of the Royal Society, B.

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.

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.

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?

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.

How to get rid of flies, part 1

This must be the most frequently asked question about flies, and although it is not really my field, I feel compelled to comment on it. After all, as much as we appreciate and admire our two-winged friends, they can be annoying to downright deadly at times. So, for those suffering from from an affliction of Diptera, here is a tentative key to fly problems I have faced.

NOTE 1: An “affliction” is more than the odd fly or two. Most fly problems are avoided by the commonsense practices of using screens on windows and keeping trash outdoors.

NOTE 2: My advice is for entertainment purposes only; I do not pretend to be an expert on fly control and I cannot respond for requests to help with fly problems. Please contact a licensed pest control professional.

Key to Fly Problems:

1. The fly problem is indoors… go to lead 2
-. The fly problem is outdoors… will be in part 2 (next blog)

2. Big grey, grey and black striped flies, or metallic blue or green flies suddenly appear in large numbers, usually attracted to the daylight at windows… Answer: 1) Something has died in or under your home (frequently a rat). Look for and dispose of carcasses. Be aware that this problem will go away in a week or two as the flies go through the food. 2) If this occurs in early spring or on warm winter days (where winters are cold), it is more likely these are overwintering cluster flies that have been “awakened” by warm temperatures. You need to seal around window casings (the usual entry point) to prevent them from entering the house.

– Smaller, less chunky flies… 3

3. Hairy, mothlike flies with broad but pointed wings (see photo below)… Answer: You have flies called moth or drain flies. Their larvae live in the accumulated sludge in your drains. Clean the drains and they should go away.

– Flies not so hairy and wings not pointed… 4

4. Small yellowish flies slowly hovering hovering over fruit, wine glasses, or open trash… Answer: Pomace or vinegar flies (genus Drosophila), also commonly known as “fruit flies”. Attracted to odors of decay, especially fermentation. Get rid of the decaying material, clean up trash, and the flies will quickly go away.

– Flies not yellow, or if yellow, run quickly and do not slowly hover… 5

5. A group of flies forming a swarm (a group of flying individuals), gently zig-zagging, always in flight in doorways, alcoves, or the center of a room… Answer: Lesser house fly males have come in through an open door or window. They are harmless and will disappear in a few hours. Window and door screens will prevent this.

– Not forming a swarm indoors… 6

6. Black-winged, tiny gnats that seem to be attracted to lights, or strangely, to the pages of a book you are reading at night. They seem to gently fly or “dance” against the pages or whatever surface. Associated with house plants… Answer: Dark-winged fungus gnats are breeding in the soil of your house plants. They are harmless, but potentially annoying. If they become unbearable, try watering the plants less, or getting rid of the most affected plant.

– Flies not dark winged, not a gentle fliers, not associated with plants… 8

8. Flies usually run, not fly, in a distinctive “stop-go” pattern. When they fly, the flight is direct, not slowly hovering. Color various, but often with yellow… Answer: Phorid flies are in your house. Either something has died in the walls, where the bigger blow flies cannot get to it, you have a sewage leak under your house, or some other situation is amiss. Call in the professionals if they are overwhelming.

– Anything that gets to here is in the category of less common “pests” that need to be diagnosed on an individual basis. Different flies affect the indoors in a variety of ways in other parts of the world. I would be happy to read any accounts that differ from what I have written here.

next blog: outdoor fly pests

Getting lucky

Collecting flies while they are mating is a surefire way to establish conspecific identity. Many female phorids are extremely different in appearance than the males (search this site for lots of examples), and linking the two together can be almost impossible, based on morphology.
< Borgmeieriphora in copula

Borgmeieriphora in copula oblique

In this case, we have a pair of Borgmeieriphora collected in a Malaise trap by Wendy Porras in Costa Rica. The females are wingless, reduced creatures, which however have a sharpened, parasitoid type ovipositor. They lived in army ant colonies, but are rarely collected. The only large series of specimens known is a group that I caught over such ants at La Selva Biological Station many years ago. The males were flying over the ants, carrying the females, as many phorids do. Since then, males have shown up frequently in trap samples, but until now females almost never. This new capture was surely a huge stroke of luck, because most mating pairs separate before they die in the alcohol.

Something “new ” for Central America

When in Brazil a few years ago, my team of Giar-Ann Kung, Wendy Porras, and I found the spiny, brachypterous (short-winged) females of phorid genus Pheidolomyia. These flies, which live in the nests of the ant genus Pheidole, were only known from Brazil. Once back home in Costa Rica, however, Wendy quickly found them there, too. This demonstrates two important principles of dipterology: 1) Wendy is a great collector, and 2) our knowledge of the distribution of tropical flies is extremely fragmentary.

A female Pheidolomyia from Costa Rica - photo by Inna Strazhnik

A female Pheidolomyia from Costa Rica – photo by Inna Strazhnik

After I remarked on yet another interesting “South American” phorid fly showing up at La Selva Biological Station during the ALAS (Arthropods of La Selva) project, the ant ecologist Jack Longino agreed with me, only partly joking that “if you collect long enough at La Selva, you get the entire Neotropical fauna!” Now, that’s a hypothesis that would be fun to test.

Phorid flies and frogs

Phorid flies are characterized by my colleague, Henry Disney, as the most biologically diverse family of insects. With each passing year, we find more and more unusual lifestyles and larval food preferences that support this statement.

Female Agalychnis spurrelli. Photo by R. Horan III


In the New World tropics, there are a huge variety of frogs found in rain forests. Many of them live in the canopy and come down to the ground level only for mating. Often they lay their eggs on leaves over water bodies, apparently to try and limit depredation by aquatic predators. This creates an opportunity for phorid flies.

My co-author, Robert Horan III, found that eggs of the gliding leaf frog, Agalychnis spurrelli, were turning a strange white color in his study on Barro Colorado Island in Panama. Further investigation showed that maggots of a small fly were eating the eggs. He reared some adults, sent them to me, and they turned out to be a new species that we named Megaselia randi. The name was a tribute to an influential herpetologist, Stan Rand, who helped Robert in his early career.

Healthy frog eggs. Photo by R. Horan III.

Infected frog eggs. Photo by R. Horan III.

This is not the first instance of phorid flies feeding on frog eggs in Latin America. Frogs in two other genera, Phyllomedusa and Leptodactylus, are also attacked. A colleague of mine recently contacted me about a frog egg feeding species in Ecuador.

Phorid larvae in eggs. Photo by R. Horan III.

There are probably thousands of species of Megaselia in the Neotropical Region, most of which are unknown, and the lifestyles of the 350 or so known species are also relatively unstudied. It is possible that among them there are a whole range of flies attacking frog eggs. Herpetologists, keep the possibility of phorid flies in your mind!

Reference: Brown, B.V. & R.V. Horan, III. 2011. A key to Neotropical Region frog-egg-feeding species of Megaselia (Diptera: Phoridae), with a new species from Panama. Contributions in Science. 520: 1-4

Phorid parasitoids of endangered ants also endangered

When ant-decapitating flies have endangered hosts, they become endangered, too. Today in the journal Zootaxa, I describe three new species of phorids found by my co-authors Marcos A. L. Braganca, Diego S. Gomes, Jarbas M. Queiros, & Marcos C. Teixeiras. The three flies attack Atta robusta, a species of ant found only in restinga (sandbank) vegetation in a small area in Brazil. Two of the flies are Eibesfeldtphora species, while the other is a Myrmosicarius; all are parasitoids developing in the ant’s head. We don’t have photos, but I am taking the opportunity to show a couple of fabulous photos of another Eibesfeldtphora attacking leaf cutter ants in Costa Rica by Wendy Porras.

Eibesfeldtphora curvinervis about to attack a leaf cutter ant. Photo by Wendy Porras.

The fly laying an egg into the ant’s head through the occipital foramen (neck). Fabulous photo by Wendy Porras.

Terrifying photos. If these flies were the size of crows we’d never leave our houses!

Home of the world’s smallest fly

The world’s smallest fly (0.40 mm long) was collected at Kaeng Krachan National Park in Thailand, the country’s largest.

It is a beautiful place with hot lowlands and misty highlands where the forests are crawling with land leeches.

There are many large mammals in this park, including leopards.

We conducted a training course for the Thai parks staff who would be helping us; here is Mike Sharkey leading the group on how to properly use a Malaise trap. The fly, Euryplatea nanaknihali, was collected by one of the many traps placed in this field.