That little scuttling thing playing peekaboo from the neck feathers of the male is actually an adult fly in the family Hippoboscidae, and most likely a male Crataerina pallida, the swift louse fly. These flies are ectoparasites of birds, where they bite and feed off the blood of both nestlings and adults.
Hippoboscids, like bat flies in the family Nycteribiidae (sometimes considered a subfamily of the Hippoboscidae) that Piotr Naskrecki has been showing off this week, give birth to live, late-stage maggots that the female has reared and nourished one at a time in her abdomen. The maggots are deposited into the swift’s nest, where they pupate and then scuttle onto their nestling host. According to Hutson (1981), fly populations peak in mid June when the swift nestlings are just beginning to hatch, and steadily fall off from there until most flies are dead by mid to late August, and he stated the flies do not make the migration with the birds.
But, since these flies don’t lay eggs, they must be spending the winters in the nest boxes as pupae, awaiting the return of their hosts year after year. Hutson found that males are more prevalent early in the spring, with females to follow. This leads us to an interesting question of how this louse fly got onto this bird! The fly was already aboard the bird when it entered the box (if you watch closely you can see a white blob that moves around neck is first visible at 0:06, immediately after the male bird approaches the sitting female). This means that one of two things happened: either the male bird has in fact carried its little parasite friend down to Africa and back (something that neither Hutson nor Walker & Rotherham (2010) believe to be the case) (and assuming this was the first nestbox that the bird stopped in, which I take to be the presumption of the ornithologists who posted the video and stated it shows a male reuniting with its mate from last year in last year’s nestbox), or alternatively, the male bird did stop for a time in another nestbox where it picked up its little hitchhiker, and then proceeded on to its longterm mate. This of course raises questions about how committed these birds really are to their mates, and whether they may be getting a little action on the side (or at least exploring their other options) before settling down for the season. Since I know pretty well nothing about bird biology, if someone knows more about swift mating, bonding, and extra-pair copulation, let me know in the comments if I’m way off.
Either way, catching a glimpse of a louse fly playing peekaboo on the neck of its host may raise more questions than the initial emotional response of “WHAT IS THAT THING?!?”, and that’s pretty darn cool.
Yesterday marked the 100th anniversary of the extinction of one of our most iconic emblems, the Passenger Pigeon (Ectopistes migratorius). The web is alive with tributes to Martha, the final individual of her species, and cautionary tales of conservation and how we should be working to prevent this happening to any other species. There has also been considerable discussion and debate recently whether the Passenger Pigeon may be a candidate for “de-extinction”; the theoretical process of bringing a species back from the void through cloning and genetic engineering. Seeing how I generally dislike vertebrates dominating the biodiversity news cycle, I figured we could all use a slightly less depressing story about extinction, de-extinction, the role of natural history museums in conservation, and of course, taxonomy.
As we’re beginning to understand, no species is an island unto itself. Every individual is an ecosystem of parasites, predators and symbionts, and thus when one species disappears, its co-dependents are just as likely to vanish, usually without us even realizing it. Allow me to share the story of Columbicola extinctus, a chewing feather mite that quietly faded into the night likely years prior to Martha’s high-profile demise on September 1, 1914, and which we only learned about 20 years after that.
Columbicola columbae, a species closely related to Columbicola extinctus (it seems the differences between them are slight modifications of the head and genitalia; feel free to use your imagination). Photo by Vince Smith, used under CC-BY license.
Working from a preserved Passenger Pigeon specimen collected in 1895 and housed in the Illinois Natural History Survey, Richard Malcomson discovered and described Columbicola extinctus in 1937, noting he had only seen 15 specimens of this new louse. In what may be the saddest etymological discussion I’ve seen, Malcomson says:
“Dr. Ewing of the National Museum, Washington, D.C., suggested the name of extinctus which surely is a suitable one for the Passenger Pigeon is now extinct and probably has carried the parasite into extinction with it.”
And so humanity carried on, parading the Passenger Pigeon out as the flag-bearer for extinction, while its lowly louse faded from memory. That is, until 1999, when, like a phoenix louse rising from the ashes of its host, Columbicola extinctus out-lived its name. While reviewing the genus Columbicola, Dale Clayton and Roger Price discovered that Columbicola extinctus wasn’t found solely on the Passenger Pigeon, but was in fact still alive and well on the Passenger Pigeon’s closest living relative, the Band-tailed Pigeon (Patagioenas fasciata)! What’s more, Columbicola extinctus was found on Band-tailed Pigeon specimens collected all up and down the Pacific coast, from California to Peru! As Clayton & Price note
“Our study reveals no consistent differences between Columbicola specimens from the extinct passenger pigeon and those from the extant band-tailed pigeon, C. fasciata. Thus, there is no longer grounds for considering this species of louse extinct, despite its unfortunate specific epithet.”
It’s worth considering how bird specimens preserved and maintained in a natural history museum allowed taxonomists to not only find a species at a time when it was believed to be extinct, but to also resurrect that same species 60 years later, redefining the term “de-extinction” before it was trendy. Sure, Columbicola extinctus’ species epithet may be a little premature, but it also serves as an important reminder that while extinction is usually forever, nature sometimes finds a way.
And should someone ever succeed in bringing the Passenger Pigeon back from extinction (however unlikely that is or may be to occur), we’ll be able to reunite two species who’s lives and legacies were intimately intertwined, and who were each thought to be lost to time and humanity. A fairytale ending if ever I’ve heard, albeit one that probably won’t make it to Disney.
— Clayton D.H. & Price R.D. (1999). Taxonomy of New World Columbicola (Phthiraptera: Philopteridae) from the Columbiformes (Aves), with Descriptions of Five New Species, Annals of the Entomological Society of America, 92 (5) 675-685. DOI:
Malcolmson R.O. (1937). Two New Mallophaga, Annals of the Entomological Society of America, 30 (1) 53-56. DOI:
Seeing how Canadian Prime Minister Stephen Harper has suddenly become a bastion for conservation biology, ornithology and science outreach with the announcement that a bird sanctuary has been named in his honour in Israel, I put together a little memento for him to hang in his office. Hopefully it will serve to remind him just how awesome birds and nature are, as long as they aren’t getting in the way of his Albertan oil field development plans, of course.
I guess in the end the joke is on me though. I’m the one spending the prime of my life fighting against the anti-science rhetoric being spewed by my elected officials to earn a PhD the old-fashioned way instead of just dismantling research divisions, field stations and libraries that don’t support my political platform!
UPDATE: It turns out my first theory involving oestrid bot flies was full of holes. I’ll leave it up because the biology of the individual parasites is accurate and interesting, but see the bottom of the post for an accurate description of what happened in the photo. I apologize for the misinformation.
Recently, I was catching up on Twitter late at night when @PsiWaveFunction shared a link to a photo on Reddit that stopped me cold in my tracks and that has kept me morbidly fascinated since. I’ve spent the better part of a day thinking about the photo, and I think I’ve pieced together the series of events and organisms that lead to the case of the mystery myiasis. If my theory is correct, this might be one of the coolest cases of parasitism I’ve ever encountered, and features a fly who’s life history beautifully illustrates the intricacies of evolution, another fly that’s threatening the birds which helped Darwin develop his theory of evolution through natural selection, and a bird who is being selected against by the worst possible luck.
Normally I’d include the photo in question right about here, but out of respect for those victims readers who are a tad squeamish at the sight of parasites (or birds), I’ll simply link to it and allow your curiosity to battle your better judgement1. I’ll give you a moment to decide and, should you accept the challenge, digest what you’ve just seen.
So, were you amazed? Disgusted? Wondering what the hell you were looking at? If you’re like me, you probably felt a little bit of all three, and then immediately went back to take a closer look.
Welcome to the wonderful world of warble flies (family Oestridae)! Each of those oddly formed lumps is actually a bot fly maggot which has burrowed beneath the skin of the chick to feed and develop. You’ll notice two dark marks on the exposed end of each maggot; these are the spiracles through which the maggot breathes. After a few weeks, each of the maggots will wriggle free from the bird, drop to the ground and pupate, eventually emerging as an adult ready to breed. Normally the host is left mostly unharmed after providing safe harbour for a bot fly, but in this case I suspect the bird might have problems due to the shear number of maggots present (at least 15 that I could make out).
Dermatobia hominis -- Photo by J. Eibl, Systematic Entomology Laboratory, USDA.
What’s odd about this situation2 is that these bot flies have parasitized a bird. You see, almost all bot flies are mammal parasites, infesting anything from rodents to elephants, and are usually very specific about their host species. One bot fly however, Dermatobia hominis, is a generalist, and has been recorded infesting a number of different animals, from humans and monkeys to dogs and cats, and of relevance to this story, birds on occasion. In a family of narrow specialists, it’s a wonder that D. hominis is such a broad generalist; until you learn how D. hominis distributes its offspring — by hijacking other flies to serve as expedited egg couriers.
Psorophora sp. (Culicidae) with D. hominis eggs attached. Illustration by A. Cushman, Systematic Entomology Laboratory, USDA.
After mating, female D. hominis will snatch up other parasitic flies, like mosquitoes, flesh flies and muscid flies3, and lay a clutch of eggs on the enlisted fly. When the carrier fly locates and lands on a host to feed4, the body heat of the victim signals the bot fly egg to hatch and fall from the carrier onto its new home, where it quickly burrows in to begin feeding. This amazing life cycle means that the female bot fly has little control over where, and on what species, its offspring ultimately end up infesting, resulting in a nearly random generalist parasite that must be able to survive on whatever host it finds itself on, including our small bird.
Obviously the natural world is a complex system, and unfortunately for our bird, it’s full of a diverse array of parasites, all looking for a free meal. Let me introduce you to another player in this saga, Philornis downsi (Muscidae), a fly native to continental South America and Trinidad & Tobago, where our unfortunate bird lives.
Philornis in nasal cavity of deceased bird. Image from O'Connor et al. 2010
While adults are unassuming, feeding on pollen and nectar, Philornis downsi larvae are brood parasites of nesting birds. Hiding out of sight during the day in the bottom of the nest, maggots emerge after dark to crawl within the nasal passages of developing chicks, feeding on their blood and tissue, sapping their energy. As the maggots continue to grow, they begin feeding elsewhere on the nestlings, causing severe damage and ultimately death. Throughout the Galapagos, where the fly was introduced sometime prior to 1964, Philornis downsi has been causing nestling mortality rates as high as 95% in Darwin’s finches, the unique birds who’s diverse beak shapes inspired Charles Darwin’s theory of evolution by natural selection. While there has been a great deal of work done on P. downsi in the Galapagos in an effort to save these ecologically important birds5, I assume it is also receiving research attention in its native range, which is where we return to Reddit, our original photo and what I think happened.
Of all the parasites, in all the nest boxes, in all the world, she flies into mine.
My theory was wrong. See below for information about the actual parasite.
A recently mated female Dermatobia bot fly was looking for a carrier fly
A female Philornis downsi happened to fly by, was quickly snatched by the bot fly and entrusted with a load of bot fly eggs
The female Philornis was released, and continued her search for a bird’s nest to deposit her eggs in
Finding a nest, the Philornis female walked around, laying eggs among the nesting material, and happened to tread across the young bird in the nest
The bot eggs, sensing the proximity of a warm-bodied host, hatched and quickly found their way to the unlucky bird’s face
The Philornis female finished laying her eggs and took off from the nest, leaving chaos brewing in her wake
Later, a social media-conscious research assistant comes along, finds the disfigured nestling, and does the only logical thing; takes a picture and posts it to the internet for all to enjoy!
Of course, this is only a theory based on a single photo and a very small fraction of information about the team’s research, but given the evidence and biology of the species potentially involved, I think it’s certainly a plausible hypothesis. There are a lot of potential fallacies in my theory, like whether the bot fly larvae are actually Dermatobia, or whether Dermatobia even uses Philornis as a vector (although it’s known to use 11 species of Muscidae), but these are the sort of questions that can be observed and tested eventually. Hopefully the researchers behind the photo will rear the maggots from the bird’s face, identify the parasites involved, and then publish their work so I can find out whether any of these ideas turned out to be accurate6.
Whether my theories were correct or not, the fact that they’re even plausible keeps me interested and excited about entomology and the intricate roles parasites play in our daily lives!
Eibel, J.M., Woodley, N.E. 2004. Dermatobia hominis (Linnaeus Jr., 1781) (Diptera: Oestridae). The Diptera Site. Accessed June 6, 2012. http://1.usa.gov/MbTexi
Fessl B, Sinclair BJ, & Kleindorfer S (2006). The life-cycle of Philornis downsi (Diptera: Muscidae) parasitizing Darwin’s finches and its impacts on nestling survival. Parasitology, 133 (Pt 6), 739-47 PMID: 16899139
O’Connor, J.A., Robertson, J. & Kleindorfer, S. (2010). Video analysis of host–parasite interactions in nests of Darwin’s finches, Oryx, 44 (04) 594. DOI: 10.1017/S0030605310000086
UPDATE June 7, 2012 @ 3:30PM EST: It turns out that the maggots in the bird’s face aren’t Dermatobia hominis, or even bot flies of the family Oestridae at all! After doing some further research, I’ve learned that they are more likely to be another species of Philornis fly. I was totally unaware that there were flies outside of the oestrid bot flies which burrow into the skin of hosts and form warbles like these, but it turns out there are.
While Philornis downsi are ectoparasites that feed on nestling birds as I described, it seems that there are several species in the same genus which burrow within the skin and form welts similar to oestrid bot flies. Here’s an example of Philornis vulgaris infesting a Tropical Mockingbird nestling from Colombia:
Philornis vulgaris infestation from Amat et al. 2007
Looks vaguely familiar no? I think it’s safe to say now that this is what happened in the original photo and not the complex tale of 2 parasites like I described above.
I’m incredibly embarrassed by my Taxonomy Fail here (which holds a TFI of 11.3). Although the biology of the two parasitic species I originally discussed are accurate, the chances of them having anything to do with one another appear to be unlikely. I sincerely apologize for publishing a story that spread such inaccurate information, and I’ll do my best to not let it happen again.
Note to self: don’t assume you know anything, especially when it involves parasites.
On the bright side, I learned something new about Diptera (and humility) today, and we can all rest comfortably knowing that there are multiple, unrelated groups of flies that get under the skin of their hosts. Because I’m sure that makes everyone feel better.
More information about subcutaneous Philornis:
Amat, E., J. Olano, F. Forero & C. Botero 2007. Notas sobre Philornis vulgaris (Couri, 1984) (Diptera: Muscidae) en nidos del sinsonte tropical Mimus gilvus (Viellot, 1808) en los Andes de Co- lombia. Acta Zoológica Mexicana, 23(2): 205-207. http://bit.ly/LwsHh1
Uhazy, L.S., Arendt, W.J. 1987. Pathogenesis associated with philornid myiasis (Diptera: Muscidae) on nestling pearly-eyed thrashers (Aves: Mimidae) in the Luquillo Rain Forest, Puerto Rico. Journal of Wildlife Diseases 22 (2): 224-237. http://bit.ly/KlXBGR
1- If you can’t decide, I vote you click and look. You can thank me later.
2- Beyond the whole face-of-a-million-maggots of course.
4- Something these blood-sucking flies have evolved to do quite well obviously. The fact that bot flies “cheat the system” in this regard, getting their eggs to their host without needing to invest energy in complex host-finding senses, just goes to show that nothing is more awesome than evolution in action.
A few days ago I was walking through the University of Guelph Arboretum taking some down time and trying to get back into the photography groove when I noticed a peculiar sight…
The trees were weeping, and dozens of flies were lapping up the sweet, sweet tears! Since there were several of these patches on two nearby trees (my tree bark ID skills are severely lacking, I’m a leaf man) and the wet marks were 4 to 10 feet off the ground, I felt it was a safe guess that it wasn’t a territorial marking (unless the UofG men’s basketball team was having a summer camp…), and last I checked I wasn’t in Fangorn Forest, so I did a little detective work to discover the story behind the sadness.
Closer inspection revealed these curious holes:
My first thought was to scan for long-horned beetles (Cerambycidae) or perhaps metallic jewel beetles (Buprestidae), but after seeing nothing but flies and wasps, I took a closer look and noticed that the holes only pierced the bark, and not the xylem (aka sapwood). It dawned on me that what I was looking at was a tricky, sticky lure set by a bird I’d seen plenty of times before in the Arb; the Yellow-bellied Sapsucker (Sphyrapicus varius). This crafty woodpecker will cause superficial injuries to a tree, and then sit back while the sap flows free. The bird will then return to the tree and pick off the insects which are feeding on the sap, as well as some of the sap itself! Clever bird…
Pretty cool biology, so I took the opportunity to see what sort of insects were at risk of becoming an early spring brunch for the hungry sapsucker.
I observed a few butterflies when I first approached the trees, but they quickly flitted away, not to return while I was there. I’m by no means a Leper (i.e. a Lepidopterist), but I think they may have been Red Admirals (Vanessa atalanta, Nymphalidae), which are one of the earlier butterfly species to be found in Southern Ontario.
There were a number of hymenopterans taking advantage of the Saturday afternoon bounty including many Ichneuomoid wasps and this fuzzy female:
This andrenid bee (Andrenidae) seemed quite content to sit and lap up the sugary sap running down the tree bark, not caring when I moved in and out trying to get a decent photograph of it’s amazing hairdo.
While the bee was busy enjoying a solitary meal, this sawfly (Dolerus unicolor, Tenthredinidae) was more than happy to share the sap with a couple of calyptrate flies (a blowfly [Calliphoridae] on the right and what I believe to be a Muscidae at the top). In fact, the calyptrates made up the vast majority of the insects visiting the tree, in some places packed so tightly you couldn’t see the tree for the flies!
The sponge-like mouthparts found in many calyptrates are well demonstrated in this blowfly (Calliphoridae, possibly subfamily Chrysomyinae). You can see the maxillary palpi sticking straight ahead as the membranous labrum and associated sclerites mop up any residual tree sap on the bark.
Another, lesser known calyptrate family was also making an appearance; the Scathophagidae. I could make out what looked to be two species of scathophagid, including this Scathophaga sp. perched nearby awaiting its turn at the sugar shack.
Not everything went according to plan on this outing however, as I made a major n00b move – I forgot to pack specimen vials! While normally I’d have a dozen or so snap-top vials in my camera bag in case I ran into something which needed to be examined at a later date and added to the University of Guelph Insect Collection, after transferring my photo equipment into my new camera bag (courtesy of the best wife ever), I neglected to throw in the vials! The first rule of entomology (besides “ALWAYS talk about entomology”) is to collect the damn specimen, and as luck would have it, I came across a fly which I instantly wanted to collect (pictured above & below).
This Tachinidae caught my eye right away, and after several attempts, I managed to get a couple of decent images. Unfortunately, tachinid flies are one of the most diverse groups of animals on the planet, and the specimen would be vital in identifying it to the genus or subfamily level on my own. A lesson learned, and needless to say I threw a couple of vials in my bag as soon as I got home!
After getting my fill of photos and not having any means to collect some specimens, I decided to pull back and let nature take it’s course. While I never saw the sapsucker, I certainly appreciated the opportunity it created, allowing me to photograph a great diversity of flies and wasps!
Today is the birthday of one of the most influential natural science artists; John James Audubon (1785-1851). Known for his illustrations of North American birds in natural settings as well as natural history notes for each, Audubon influenced many generations of naturalists, including Charles Darwin. My grandparents hung two large reproductions of plates from his Birds of America series in our family cottage, and they are some of my earliest memories regarding art.
As an homage to John James Audubon, I thought I’d share a photo of the American Kestrel.
American Kestrel - Falco sparverius
Audubon included this species in his account, and it’s one of my favourite images.
This isn’t an insect you say? You’re right; I’m using this Cedar Waxwing to distract you from the recent lack of posts. I’ve been juggling several pressing issues (thesis writing, ESO business, deadlines for external projects, you know the deal) and the blog has been the ball that got bobbled lately. Don’t worry though, I’ve got a couple of important topics lined up to discuss in the near future! Until then, enjoy this symbol of urban Canadian winters, and check back soon for an examination of Canadian Biodiversity Science!
I think from now on I’ll stop forecasting when my next blog post will be as I don’t seem to be hitting many deadlines! Although slightly delayed, today I’ll be sharing some of the more “cuddly” creatures that we encountered during our 2 weeks in the Bolivian Amazon.