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.

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!

Worlds smallest fly discovered

In a paper appearing today, Monday, July 2, 2012, I describe the world’s smallest known fly. It was collected during the TIGER (Thailand Inventory Group for Entomological Resources) project, funded by the National Science Foundation with the grant to Dr. Michael Sharkey of the University of Kentucky and me (as co-PI).

Many stories about small things, especially parasites, quote Jonathan Swift:

“So, naturalists observe, a flea
Hath smaller fleas that on him prey;
And these have smaller still to bite ’em;
And so proceed ad infinitum.”

In this case, the quote is especially apt, because the newly discovered worlds smallest flies are parasites!

The smallest fly in the world is a member of the family Phoridae, and is one of the “ant decapitating flies”. Adult females lay an egg in the body of an ant, and the resulting larva feeds in the ants head, eventually causing the decapitation of its host. Some of these flies are being used to attempt biological control on imported fire ants, and were even featured on an episode of the popular television show “King of the Hill”.

Because these flies usually develop in the head of their host ant, they are smaller than their hosts. One would think that the smallest ants would be therefore immune to these nasty parasites, as their heads are vanishingly small. But the world’s smallest fly is one of these ant killers, and at the astoundingly small body length of 0.4 mm, these flies can probably decapitate ants with heads as small as 0.5 mm. That is pretty close to the smallest size that ants can get!

When we think of animals that are small, usually a fly or a flea come to mind. Let’s forget about fleas; they are comparative monsters at around 1-2 mm in length. But what about flies?

The common house fly is something that we think of as being small. In the world of tiny insects, however, they are virtual Godzillas at a whopping 6 mm.

Many flies are much smaller than this. Fruit flies that you see hovering over overripe bananas, for instance, are about 2 mm long, one third of the size of the “giant” house fly.

Some of the biting flies are much smaller than this. One aptly named family of flies has the common name “no see ‘um”, because of their almost invisibility when they are biting you. These flies are getting really small, usually around 1 mm in length.

The world’s smallest fly is 0.4 mm in length. Here is a microscope slide, 1″ x 3″ size, with the holotype specimen of the fly mounted on it. It’s unimaginably small, smaller than a flake of pepper you shake out of the pepper shaker.

holotype specimen of Euryplatea nanaknihali Brown

Do you see it, within the small circle, to the right and slightly above center?

The world smallest fly doesn’t really look like a fly. It’s one of those weird phorids whose body form we call “limuloid”, after Limulus, the horseshoe crab. It is a defensive body form that allows the flies to live in the ant nest which, based on this body structure, is probably part of the fly’s life. It has short wings, but they are functional sized, so this fly could easily fly from ant nest to ant nest. It also has a sharply pointed tip of the abdomen, indicating that it is a parasitic species.

My research is funded by the National Science Foundation, currently grant No. DEB-1025922.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.

Keep your eyes on the flies

[This is a guest post by Lisa Gonzalez, one of my field team members.]

Lisa Gonzalez in demonstration mode

Lisa Gonzalez in demonstration mode

Last week I had the incredible honor of joining a small team that included Wendy, a parataxonomist; Inna, a scientific illustrator and videographer; and Kat, an accomplished amateur photographer; under the guidance of the respected Dipterist Dr. Brian Brown, to the lush lowland tropics of Costa Rica on a phorid fly foraging expedition. Our goal was to record and observe parasitic phorid fly behavior– in particular to begin unraveling the mysteries surrounding certain phorid flies in the genera Apocephalus and Dohrniphora— as well as collecting any specimens that struck our interest.

My first trip to this beautiful, magical country was 10 years ago, but every day that has gone by since has been a day that I have anticipated returning. So suffice it to say I was beyond excited at the prospect of spending entire days under the forest canopy, scanning the ground and leaves for parasitic phorids and their specific hosts.

People who know me know that my passion for insects runs deep, but I still get an occasional incredulous glance, a slightly furrowed brow or a polite smile and shrug from my non-entomologist friends as I explain that the vast majority of our trip will be dedicated to looking for 3 mm sized flies (even though they know it is part of a scientific project, as in, WORK.) No zip lines, no sipping mango margaritas on the beach –sugar on the rim, hold the salt!– no waiting for a quetzal to fly by for that perfect photo op.

No, my friends, we will be looking for flies, cool parasitic ones, because they are out there, lurking in the jungle, waiting for someone to observe them doing things that are infinitely more fascinating to me than the showiest toucan or the noisiest oropendola. Somebody needs to give them the attention they deserve!

After a morning cup of that fine, fine Costa Rican coffee, we used the help of the phorid flies themselves, namely their incredible ability to detect the alarm pheromones of their hosts. We searched the tree trunks and undergrowth for the specific types of ants that serve as the hosts (Odontomachus sp. and Paraponera clavata in this case) so that we could collect them, crush them, and thus attract the flies we so anxiously sought, a technique that Brian serendipitously but no less ingeniously discovered 20 years ago.

As the flies started to hone in on the chemicals released by the distressed ants, I felt myself becoming completely entranced by the miniature drama unfolding at my feet. This is the point where I struggle to find my mental middle zone, maintaining a focus on the flies while not becoming too tunnel-visioned; still being aware of my surroundings since, after all, we are in a jungle with stinging ants and wasps everywhere, and an occasional venomous snake, but most importantly, not wanting to miss any phorid action on the sidelines.

Keeping your eyes on the flies and not being distracted by bedazzling morphos or adorable sloths (my goodness, they ARE cute!) reaps great rewards for anyone with even a modest interest in animal biology and biodiversity. For an entomologist, or those willing to scale down their perspective and peer into the microcosmos, it is a truly awesome experience to see a minute female fly risk her own life by attacking an ant at least twice her size, desperately needing a place to lay her egg (or eggs), using a variety of bodily tools, such as ovipositors shaped like sabers or mouthparts serrated like knives. These females are so alert and nimble, like little ninjas, and although the outcome of their efforts, which results in decapitation or an “‘Alien’ chest burster” style host death depending on the phorid species, may seem cruel to our human sensibilities, I see a brave and resilient mother struggling to care for her young (that’s a whole lot of anthropormorphism for one sentence, I know!)

Brian decided to expand our efforts in the field on this trip by collecting female phorids and hosts and observing them in captivity in our make shift lab. He very generously put me in charge of this part of the project, proclaiming that I am “good at keeping bugs alive” from my years spent as the museum’s insect zoo technician, a professional extension of the top secret insectary I kept in my closet when I still lived with my parents many years ago. After several days of working out humidity issues, adding extra masking tape for the sneaky escape artists, and trying to provide a stress free environment for the flies to “go about their business,” we were able to observe some provocative behavior in captivity. Some preliminary work was done with the species Dohrniphora conlanorum, and we successfully reared larvae of Apocephalus paraponerae. I was alone in the lab when I first spied the chubby little bundles of maggot-y joy in the abdominal cavity of the Paraponera ants, and in my solitude was able to get up and do my celebratory maggot dance without shame. The pure excitement over seeing a world that most people rarely stop to notice, the thrill of something new on the other end of your scope, is greater than a million zip line adrenaline rushes or brain-in-a-jacuzzi delicious tropical rum buzzes to me. I am so elated to have been a part of this project, and I hope you enjoyed my attempt to briefly describe that elation. Now to start counting the days until I return once more…

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

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.