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.
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.
I call these “miracles” not in the religious sense, but in the unlikelihood that I would notice them in a “normal” sample with all the macro-garbage obscuring them.
The first is a male, perhaps of the genus Metopina, with the thick costal vein almost as long as the wing.
Next is a bizarre female termitoxeniine that has not yet shed its wings.
A relatively “normal” wingless female Chonocephalus.
Finally, a flattened male of a new phorine genus with a short costa.
And I still have many more vials to look through! Life is good.
All photos were made by Inna-Marie Strazhnik, who is a superb artist.
I am sorting through a bunch of Malaise trap samples from Thailand from which all the insects larger than about 2 mm have been removed. The absence of larger insects makes all the tiny ones stand out, so these samples, the “microfraction” are golden. They are full of treasures: usually overlooked tiny things like Chonocephalus, termitoxeniines, and weird Metopina group males. I’ll publish more photos soon, but here are a couple I photographed previously.
Note the shieldlike crest on the back of the head in the second photo. Totally bizarre.
Microfractions represent yet another largely unexplored frontier of tropical phorid diversity. After nearly 30 years of doing this, I can still be amazed and awed by “my” flies.
Firstly, such spiny flies are almost invariably found in species associated with ants, especially army ants. As evidence for this, here are 3 flies from the New World tropics found with Labidus army ants: Acontistoptera, in which the long setae (bristles) are found almost only on the wing rudiments, Adelopteromyia, which are spiny on the wing and on the body (especially the head), and Xanionotum, which has multiple rows transversely across the abdomen.
The large setae could be used to fend off attacking ants, like a porcupine, or for sensory purposes in the darkness of underground ant colonies. Or both. One thing to keep in mind is that the flies probably can move the setae, erecting them or laying them down. They are much more flexible, mobile, and speedy than you might think, as they literally runs circles around the host ants.
My friend in New Zealand, Hugh Oliver, saw the picture of the wingless female phorid in my last blog post, and asked for more photos of weird phorids. I didn’t even know he was looking at my blog, but just for him I am posting this photo of an extremely bizarre specimen we found just this week in material from Thailand. I think it is a female of the genus Rhynchomicropteron, but if so, it is an extremely unusual one! Thanks to Lisa Gonzalez for pointing it out to me, and Inna-Marie Strazhnik for photographing it. Maybe it can be number 16 in Terry Wheeler’s posts about why flies are great.
[This is a guest post by Lisa Gonzalez, one of my field team members.]
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…
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.
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!
Today is our last field day for this trip. There is still time for another dream to come true.
Being in the field, it is hard to ignore the biting flies. Mosquitoes, black flies, horse flies, sand flies, and no-see-ums all make their mark. Sometimes I forget, however, that humans are not the only recipients of their unwanted attention. For example, my good friend Dr. Art Borkent studies a group of flies called the Corethrellidae, whose mosquito-like females feed on frogs and are attracted to frog calls. But Art’s main study group are the aforementioned no-see-ums, technically known as Ceratopogonidae. The many species of these minute flies have differing ways of life, as some are predators of other insects, some are misery inducing biters of vertebrates (especially on beaches, where they can clear the humans out during certain times of day), and surprisingly, some feed on the “blood” (haemolymph) of other insects.
We saw a spectacular example of this yesterday here in Costa Rica. We took a day trip to a spot called Las Minas, where we were looking (mostly unsuccessfully) for different ant-decapitating flies. While searching around, Wendy Porras, our Costa Rican colleague, found a katydid with something strange on it. Being an excellent field biologist, Wendy immediately recognized that this white, almost pea-sized attachment to the katydid’s abdomen was a swollen female ceratopogonid, full of eggs.
I hope Art will forgive me, but I didn’t collect the specimen. I got distracted by other things, and by the time I thought of it, the fly had already left. This is a case of bad field work on my part. Certainly when significantly unusual things are seen, they should be collected so that the specimens accompany the life history observations. Hopefully we can make up for it with even more significant observations on the phorid flies that we came here to study.
[Thanks to A. Borkent for a couple of corrections to the original post]
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.
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.
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.