Category Archives: Phoridae

Army ant raid of my dreams

I suppose most people have anxiety dreams, in which things are going horribly wrong because, in their dreams, they are late, lost, without something vital, or otherwise unable to figure out what’s going on. Being an entomological geek, and obsessed with field work, my anxiety dreams are often centered around being in a great tropical place, surrounded by social insects like ants and bees, but not having collecting equipment, having to leave, rain starting, and so on. I wake up frustrated, hoping that next time I’m in the tropics none of these things happened to me.

A couple of days ago, we pulled off the road in an area known to the locals as “Bambu de Suerre” and walked on a short rocky path into the forest. We were collecting for a while at a nest of Pheidole ants, when I decided to walk further up the trail. I started to hear the sound of the distinctive ant birds that follow army ant raids, and sure enough came across a massive raid of Labidus praedator.

Associated with these ants was a huge assortment of flies, in incredible numbers. Clouds of tachinids and conopids (Stylogaster) were buzzing around the undergrowth, while closer inspection showed that there were equivalent masses of phorid flies a few millimeters above the ground, attacking the ants. We were collecting 5 or 6 flies per aspirator attempt without even looking, just waving her aspirator is blindly around the ants and sucking in air. We collected hundreds of flies, truly an amazing event, and one I have rarely been lucky enough to stumble upon.

a small part of our fly catch

The flies included several species of Apocephalus ant decapitating flies, with the most common being A. praedator. As well, we collected some highly host-specific phorid genera like Cremersia that are associated strictly with non-Eciton army ants. One of the amazing things about Cremersia is that their ovipositors are complicated and asymmetrical. We don’t know how they use them, but they are so unusual that the females were originally described as males!

female Cremersia

Today is our last field day for this trip. There is still time for another dream to come true.

In Costa Rica, II

We have had quite a bit of rain so far, nothing you wouldn’t expect in a rain forest, but it makes collecting an episodic affair. The light traps run every night, however, even in the pounding rain. So far (after one night), they have turned up two interesting flies.

The first is an acalyptrate, perhaps a lauxaniid, with interesting lines of color along the wing veins. I don’t know how unusual this is, since I don’t work on lauxaniids, but I have never seen anything like this before.

bad photo of a lauxaniid in alcohol

The second interesting thing is a female bee killing fly, genus Melaloncha, from a group that I have worked extensively on. Bee killing flies are parasitoids that attack stingless bees, introduced honey bees, and bumble bees. They are found throughout the Neotropical Region, except for Chile, and attack their hosts either at flowers or at colony entrances. I worked for years on these flies, and have described many new species. In order to collect them we had to learn a lot about their natural history, the most are active only in bright sun in the warmest parts of the day. But there is also a published record from Panama of them attacking nocturnal sweat bee.

Melaloncha

Could this be one of those nocturnal bee killers? Perhaps, and this is one of the great things about using a “new” collecting technique in the tropics-finding different things even in groups you have worked on for many years.

New frontiers in Costa Rica

Tapanti NP

My late colleague, the hymenopterist Roy Snelling, used to ask me disdainfully, “why go to Costa Rica; everything is already known from there.” Even Roy knew, however, that this wasn’t true. His mistaken assertion was that so many people had collected in CR that, given the large number of other places that had not received any attention, it would be a waste of time to go back to a small Central American country.

I disagreed with his statement for many reasons. First of all, there aren’t enough dipterists on the planet to make even a tiny part of CR “overcollected.” There are so many habitats and microenvironments in a country with a mountain range down its center in the tropical zone, that doing an inventory of all of Costa Rica is probably impossible. From dry tropical forest in the northwest to the near treeline heights of the Cerro de la Muerte, and all the rain forest inbetween, CR is a biodiversity paradise.

But more interestingly, it is possible to find new frontiers in the same sites by using different collecting techniques. Last year, for some reason, we decided to try blacklight collecting in Costa Rica for the first time since my trips in the 1980s. We used a trap of my design that was so successful, I decided to write it up for publication (watch for it in Entomological News).

Using this “old” technique again, we managed to wring out some incredible specimens of Phoridae and one special sphaerocerid from a mid-elevation site from which we otherwise had no special expectations.

For phorids, our technique yielded new specimens and a new species of a genus previously known from only a couple of females from elsewhere in Costa Rica. This genus is marked by incredible huge palps with outrageously long apical setae. Additionally, we got some parasitic phorids I had never seen before, as if we had gone to an entirely new continent. Believe me, I have gone through hundreds of samples Costa Rica, and have looked at least 50,000 specimens from this country, so when I see a congregation of new things, I take notice.

the phorid with huge palps - a fuzzy photo

The sphaerocerid was the second known specimen and species of the genus Podiomitra of the incredibly rare subfamily Homalomitrinae. Although I’m not an expert on these flies, I knew as soon as I saw it that it was something special.

Podiomitra sp.

Bottom line: we have to keep trying new collecting methods, even if they are old collecting methods. I’m going back to Costa Rica at the end of February, and I’ll be bringing my lights again!

How we started working on “rare” bee-killing flies

The most beautiful phorid flies are in the genus Melaloncha, also known as bee killing flies. I have no small bias in this statement, however, since I worked on them for several years and grew to be very fond of them.

Melaloncha punctifrons, female

One of the allures of these flies was their rarity when I first started. In all of the collections I surveyed, I could find only a few specimens, about 100 in total. There were many new species among these specimens, however, so I knew that the 32 described species was only the tip of the iceberg. But how was I to uncover the rest of that iceberg?

Many parasitic phorid flies seem to be attracted to masses of their hosts. Logically, aggregations of hosts should create aggregations of parasitoids, so Giar-Ann Kung and I decided to try to make aggregations of stingless bees, the known hosts of these flies. Monty Wood, a fellow dipterist who works on tachinid flies, told me that when he sprayed a mixture of honey, Coca-Cola, and water onto undergrowth vegetation in an attempt to attract his flies often attracted huge aggregations of stingless bees instead. Therefore we tried spraying honey and water, and were almost immediately successful in attracting bees, and eventually flies. There was one other required condition, however: it had to be in the sunlight, or the flies would not be attracted. This is contrary to most phorids, which tend to be more active in shade.

Melaloncha acoma attacking stingless bee

Once we adopted the honey spray and sunlight combination, we started collecting large numbers of these flies, eventually collecting thousands of them. Sometimes, we were almost too successful in attracting the bees, producing gigantic aggregations that made it impossible to breathe or see anything, necessitating the use of jury rigged bee veils. These consisted of an insect net placed over the head and sealed around the neck with rubber bands. Eventually, though, the tiny stingless bees would get in, and we’d have to beat a retreat to get the annoying things out of our eyes, ears, and noses.

Me wearing a jury-rigged "bee veil" in Argentina, 2003

It was all worth it though, as we ended up catching 50-100 Melalonchaper day at good sites, and found almost 150 new species. I think there are still many more out there to find, so we keep spraying honey wherever we go in the tropics, and keep finding the beautiful, but deadly (to bees) bee-killing flies.

Melaloncha xanthocauda, femal

Melaloncha berezovskiyi, female

Melaloncha acoma, female

Take your watch to the field

I am sure it makes perfect sense to bring your watch into the field to keep track of the time. That is not why I am advocating this practice, however. A watch once helped us make an important new observation on bee parasitizing flies in the tropics.

One unavoidable fact of tropical fieldwork is that you will stink. You sweat your clothes out within the first 10 minutes after breakfast, and remain damp and moldy all day until you hit the showers. It is impossible to wear clothes for more than one day without them getting rank and disgusting. You can either bring enough clothes to change all of them every day, do lots of laundry during the trip, or resign yourself to having some of your clothes remain not suitable for indoors and fine dining.

Things that you wear or sweat on day after day buildup in particular fragrance. For instance, my collecting bag is always covered with butterflies in the field, probably because they mistake it for a piece of carrion. Other items can be the same way.

My collecting bag swarming with bees, flies, and butterflies. It stank.

In 2001, Giar-Ann Kung and I were in Colombia with some colleagues, and it was incredibly hot and humid. We were after bee killing flies of the genus Melaloncha, which we were trying to attract with honey. Placing honey on the undergrowth attracts large numbers of bees, and once we had large numbers of bees, we hoped that the parasites would arrive as well. Problem was, it wasn’t working. The bees were much more attracted to Giar-Ann’s watch, which really stank. She took it off and put it on sheet that we had placed in the field and the bees visited it avidly. Suddenly, against the black background of the watch, Giar-Ann noticed a tiny yellow shape curling its abdomen and running towards tiny bees. She collected the fly and showed it to me – it was a female Styletta crocea, a rarely collected species whose lifestyle was completely unknown. I doubt if we would ever have seen the fly without the black watch in the background. Later, we collected Melaloncha specimens, but that Styletta was our first big break of the bee parasite project.

female Styletta crocea

It never ceases to amaze me how events unfold during a research program or field trip. No matter how much you prepare, invariably which you thought would work doesn’t, but something completely different appears or is found. It’s part of the reason why fieldwork and research remain compelling and exciting for those of us who aspire to make new discoveries.

A new parasitic phorid in honey bees

Female Apocephalus borealis specimen

Lots of press coverage is swirling around our recent paper in PloS ONE: “A New Threat to Honey Bees, the Parasitic Phorid Fly Apocephalus borealis”, available here . Note, I use the term “our” advisedly, as I am 7th of 10 authors, and thus cannot take much of the credit for this work! Unfortunately, some of the press coverage this publication is garnering is incorrect, but I’ll let my colleagues at UCSF handle that on their website. What I’d like to concentrate on is the phoridological context of this story, particularly on the genus Apocephalus.

Genus Apocephalus consists of about 300 described species, virtually all of which are found in the New World. I am pretty sure that species described from other regions do not belong in a group with the rest of Apocephalus. In the 1990s, I revised about half of the genus, describing over 200 new species, but there are still many more out there. Right now I have a grant from the National Science Foundation to revise the rest of them.

Current classification of this group places the species in 2 subgenera: Apocephalus and Mesophora. Species of subgenus Apocephalus are the original “ant decapitating flies” like the ones I videoed in Brazil a few posts ago. Subgenus Mesophora have very different hosts, however. Most of the known species are parasitoids of fireflies and soldier beetles, an extremely different group of hosts from the ants the others attack. In addition, I have described a few species that attack stingless bees in the tropics.

One species always stood out, however, and that was Apocephalus borealis. This crazy thing had been reared from bumble bees, yellowjacket wasps, and a black widow spider! It seems as though A. borealis has an extremely wide range of host acceptability. Perhaps this is what allows it to switch into new hosts, such as honey bees. We know that honey bees were not the original hosts, because they are an introduced species in North America. Probably bumble bees are their main hosts, but who knows? This species is only recorded from North America.

My colleague, Dr. Paul Smith, and I are currently studying the relationships among species of Apocephalus using molecular characters (DNA sequences), as well as morphology (body structure). Once we have a good phylogeny of Mesophora, we should know more about how the flies have shifted hosts through the group.

Apocephalus borealis on bumble bee, photo by K. O'Harrow

Of course, besides many new species to be discovered, many described species do not have any studies about their way of life. Particularly intriguing are some species from Costa Rica that seem to be closely related to A. borealis. Perhaps they are parasitoids of tropical bumble bees, but nobody has studied this yet.

One other thing to note: Apocephalus borealis is far from the only phorid that parasitizes honeybees. In South and Central America, many species of Melaloncha bee killing flies will attack honeybees, and we have even seen the tiny, 1 mm long Styletta crocea trying to attack these relatively giant hosts. Finally, Pseudohypocera kerteszi is an occasional past in honey bee nests, although they are much more prevalent in the nests of stingless bees. I will write more about these other bee parasitoids in future blog posts, but you can see photos of the flies on my website phorid.net.

In summary, it’s great that some phorids are getting press, and I’m sure we are going to learn a lot about this species because of its agricultural importance. Kudos to the (other) authors for their fascinating work. Don’t forget, however, that Apocephalus borealis is only one of about 4000 described species, and many more have amazing life histories still to be discovered.

A living fossil from South America

Vladimir and I sorting in the field

Hard-core dipterists know all about Sciadocera, the Australian and New Zealand fly that seems to bridge the gap between platypezids and phorids. It was immortalized by the drawing Harold Oldroyd included in his 1964 book “The Natural History of Flies” which was entitled “the most wonderful fly in the world”.

Less known is the New World species, found in South Chile and Argentina. Called Archiphora patagonica, this species is similar, but smaller than Sciadocera, and more brown in color. Hennig described a second species of Archiphora from Baltic amber, and declared that genus to have been once widespread, and now relictual in the southern hemisphere. A few years ago, I re-examined the Baltic amber fossil and showed it was probably not congeneric with A. patagonica. There are, however, three species of Baltic amber Sciadocerinae (the group is now considered part of the Phoridae), and others possibly from older amber, so it is reasonable to refer to the two living species as “living fossils”.

Elvia and Vladimir getting discouraged


I needed to collect fresh specimens of Archiphora patagonicafor a molecular project in which Dr. Paul Smith and I are trying to understand the phylogeny of phorid flies using DNA sequences. A couple of years ago, I went to southern Chile with two assistants: my old friends Vladimir Berezovskiy from here in Los Angeles and Elvia Zumbado from Costa Rica. Together, we spent three weeks scouring the forests looking for this fly. We ran Malaise traps in sites where Canadian hymenopterist Masner collected some in the 1980s, with no luck (we knew we weren’t catching them because we sorted the samples in the field, looking for the flies). Since Masner also did a lot of sweeping, we swept for hours in forest undergrowth, dumping our net contents in a bowl of soapy water and searching for the elusive flies. In a fit of inspired desperation, Vladimir even grew a beard like Masner’s to try to appease the phorid gods. We collected at a number of sites on the mainland, as well as on Chiloe Island, where we found most of the forests that Masner collected in to be gone. We even looked up the former farm of Chilean entomologist Luis Peña, where the remains of his field station still exist, and swept there extensively. We got a lot of interesting phorids, but no Archiphora patagonica.

Peña's farm

At least, that’s what we thought until we got home. When I went to the samples with a microscope, I was elated to find a single male specimen from Peña’s old farm that eluded our field sorting. Although we eventually ground the specimen up for sequencing, we took some nice photos of this fly, which show that it too is one of the “most wonderful flies in the world.”

our single Archiphora specimen

Brazil expedition: day 4

As many of you know, I work on phorid flies, including those known as “ant decapitating flies”, genus Apocephalus. These flies dart down at their hosts, laying an egg in the host body (usually the head). The egg hatches, and the resulting larva feeds inside the ant’s head capsule, consuming about all of the contents of the head. Now, the inside of ants head is not like yours or mine, full of brains; instead, they have huge muscles inside their head capsules to move their massive mandibles (mouthparts). The insect brain is an insignificant little shred of material compared to ours. Anyway, the larva feeds, and eventually the ants head falls off, sometimes before the rest of the body finishes walking around – hence the name “ant decapitating fly.”

There are almost 300 described species of these flies, but we think there are perhaps 200 or 300 more. Therefore, we’re down here collecting, and trying to understand some life history information. We were able to solve one little mystery on this trip.

A couple of years ago, we saw workers of a species of the ant genus Pheidole being attacked by an Apocephalus species, in which the flies seemed to be darting at ant larvae, rather than the adults. We saw the same thing here, and studied it in a little more detail. We even got some video of the flies 

We cut open an old dead log and found a nest of Pheidole. In short order, we had dozens of flies attracted to this exposed colony. We saw the flies darting at the ants when they were carrying larvae, as in our previous observation. We saw, however, that the flies were actually attacking the ants, and not the larvae.

The ants seem to be quite aware of the presence of the flies, and keep their mandibles in the air apparently trying to snap and grab the flies. The ants are highly agile and fast, so this seems to be a formidable defense. Apparently, the flies wait until the ants pick up a larva or pupa before attacking them, as their defense is neutralized when carrying a burden. This seems to me an amazing behavioral adaptation, but it might be commonplace, given our poor understanding of ant/parasitoid interactions.

Brazil expedition: day 3..

Actually we are farther in than 3 days. We are staying in a town called Monte Negro, and have 2 collecting sites: one about 10 km from here, and one about 50 km from here.

On day 3, we went to the 50 km site for the first time. It was seething with insects, from butterflies and uraniid moths to stingless bees and higher flies. We put up 3 of our Townes style Malaise traps, while my colleague, Dalton, and his 2 students put up a huge Gressitt-style, double headed trap. Instantly, this giant black trap became a drawing card for the local insect population. The trap was literally heaving with all the insects inside it and coating the outer surface. Rather than wait for the insects to possibly fly into the collecting bottles, Dalton swept them with an insect net. He made impossibly huge collections of tachinids, syrphids, strats, and myriads of smaller flies.

Dalton sweeping out his trap

I sat down beside the trap, and took a few photos without moving; you can see the diversity of fabulous larger flies here in the following photos.

syrphid fly

for Chris Raper - how is this for tachinid density?

tachinid fly

another tachinid fly

yet another tachinid fly

a final tachinid fly

It is unusual to see such overwhelming diversity, but sometimes it happens. We went back to the same site yesterday and all of our traps were stuffed full to the top, mostly with unwanted Lepidoptera. These we had to laboriously remove from the samples to find the more interesting (to us) material, a process that takes hours upon hours.

As for phorids, we found lots associated with ants, but the best phorid so far was in a Malaise trap sample. The attached photo isn’t the greatest, but it is the best I could do in the field with the fly less than 1 mm long. It is a male Brachycosta, the first I have seen.

tiny male of Brachycosta

Next post: a new discovery in ant decapitating fly behavior.

Brazil expedition: day 1

forest across the Rio Madeira

Actually, this is day 2, but it is day 1 of collecting. Yesterday, we (Giar-Ann Kung, and I) arrived at the same time as our Brazilian colleagues: Dalton Amorim, Danilo Ament, and Paula Riccardi. We did our shopping in Porto Velho, got a hotel, went out for dinner, and got ready for the next day.

Our main base for collecting in Rondonia is at Monte Negro, about 50 km from Ariquemes, but this wouldn’t be open to us until later in the day (it’s a Sunday). Dalton’s idea was to drive across the Rio Madeira and collect on the other side. This is particularly interesting to do because the Rio Madeira is a conspicuous breaking point for the distributions of many Amazonian creatures. Thus, on one side of the river you should get one species, and on the other side another.

unfinished bridge over the Rio Madeira


We were game, but there was no bridge. Seems the bridge is under construction, so we took a barge driven by a tugboat across the river as a ferry. On the way across we saw one river dolphin.

ferry

We also saw lots of forest destruction. Rondonia is still one of the frontiers of Amazonia, but it’s going fast. We were a skeptical that we would find decent forest close to Porto Velho. When we got across the river, however, we saw on our right quite a bit of good-looking forest. We pulled over to the side of the road to a small building in order to ask permission for access to this forest. While Dalton was in the building, another car pulled up beside us, and it turned out to belong to the owner of the site. Dalton talked for a few minutes to this very friendly fellow, who was more than happy to allow us to have access for our collecting.

We drove on a dirt road for just a couple of kilometers before stopping in some pretty decent forest. According to the owner, there were monkeys, tamarins, and other mammals still in the forest; sadly, however, the site was slated for urban development.

most of our field team


We put up two Malaise traps, and then collected there for a couple of hours. Danilo found an ant nest in a rotting stump, and collected some phorids there. The ants turned out to be a Pheidole colony, from which we got 2 to 3 species of Apocephalus ant decapitating flies. Danilo also found a colony of Dolichoderus ants, from which we collected two Microselia females, a relatively rarely collected parasitoid genus.

All too soon, it was time to leave. We packed up everything except the Malaise traps, which we left to collect, went back to the hotel to clean up, and then did the 3.5 hour drive to Monte Negro. We’re going back to the other side of the river for a couple of days on our way back, though. It’s a great spot, full of diversity, and we might as well salvage some of what’s there before it’s all destroyed.

Tomorrow: our 1st field day at Monte Negro.