Nov 272015

American Thanksgiving not only marks the beginning of left-over turkey sandwich season, but has also come to represent the official start of the Holiday Season™. Traditionally rung in with the rampant purchasing of sale-priced items, the beginning of Holiday Season™ is now celebrated instead with Black Fly Day. This year, in preparation for ugly sweater parties and more family gatherings than should ever occur in such short succession, I present to you 6 fun facts about black flies that will keep your friends and family utterly enchanted!

Simulium sp from Ecuador Black fly Simuliidae

Simulium (Psilopelmia) bicoloratum from Ecuador (Simuliidae) feasting on my blood.

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Nov 282014

When identifying insects, the further you want to identify them, generally the smaller the morphological characteristics you need to look for are. For instance, to recognize the taxonomic order Diptera, you need only count the number of pairs of wings an insect has (usually…), but to identify a fly to species, you may need to hone in on the presence or absence of a single bristle on its thorax, or middle leg, or genitals. But what about species or populations where even these characters may be too similar to confidently tell distinguish, and where you could potentially be overlooking and unknown amount of diversity, better known as the elusive cryptic species? Well, you could look at their DNA, and try to see if there are any differences there, or, if you work on black flies, you could literally look at their DNA. Like, actually looking at the shape and patterning of their chromosomes, specifically special clumps of DNA found in larval black flies called polytene chromosomes.

Polytene chromosomes are the jumbo-sized versions of normal chromosomes only found in cells involved with secretion, and for whatever reason, are only present in springtails (Collembola) and true flies (Diptera). Rather than replicating and then splitting themselves up amongst a series of daughter cells like normal chromosomes, polytene chromosomes replicate themselves over, and over, and over again, sticking together in clumps of hundreds to thousands of complete chromosomal strands all woven together into a thick rope of genetic instructions. By banding together like this, these special chromosomes reveal all kinds of fascinating information about species and speciation.

Starting in the 1930’s, while scientists were only just beginning to understand what chromosomes were and the role they played in genetics and heritability, dipterists began to notice that polytene chromosomes provided an untapped source of morphological characters to work with. Black fly taxonomists in particular latched onto this new dataset, largely because these over-sized chromosomes were easy to find in the silk glands of larval black flies, and provided a simple and low cost means of identifying species. Patterns of black and white bands, the locations and sizes of bulges, blisters, and rings of Balbiani all appeared to be conserved within populations and species, and with only 3 chromosomes to deal with, taxonomists, already tuned to look for the slightest differences and similarities between specimens, began to find all kinds of useful information; specific banding patterns that would be inverted in some species, but not in others; whole arms of chromosomes getting spliced onto the “wrong” chromosome; all three chromosomes getting jumbled up and stuck together in the middle like a genetic pinwheel with what they called a chromocenter.


By studying these “macrogenomes”, Simuliidae experts have been continuing to refine what a black fly species really is, and are beginning to unlock the mysteries of cryptic diversity.

Take, for example, work recently published by a group of black fly experts on the Old World subgenus Simulium (Wilhelmia). These flies originally came to the group’s attention due to an outbreak of black flies in Turkey which was driving down livestock production and tourism due to the sheer numbers of biting adults (those in Northern Canada can surely commiserate), and in order to figure out what species was responsible, decided to take a closer look. A much, much closer look, specifically at their polytene chromosomes.

After sampling larval black flies from across Europe, they discovered that what had recently been considered one generalist species found from England clear across the continent to at least Kazakhstan, Simulium (Wilhelmia) lineatum, was actually at least 3 species, each with unique differences in their chromosomes, and which replaced each other in streams as you head East!

Here you can see where the “actual” Simulium lineatum is found (blue) (although the authors note that something funny may be going on with the English specimen’s chromosomes, which could lead to further splitting), and where each additional species crops up as you move east, with Simulium balcanicum in green, Simulium turgaicum in red, and Simulium takahasii in yellow. The orange area without any data points is a void in the team’s data, but they have reason to suspect that several species recently described from China will fit into the pattern discovered in the west. Now that the team has worked out these basic limits for each species, they also hope to explore whether or not these species may be successfully mating with one another despite the differences in their chromosomes, or whether hybridization can occur between species pairs. All of this new information will in turn help us understand the intricacies of polytene chromosome taxonomy further, and continue to adapt black fly taxonomy to fit the total evidence available.

So by peering deep within the silk glands of black fly larvae, we can now weave together the ways in which simuliids diversified, and begin to understand the web of underlying mechanisms that make one species become two, or three, or more. It just goes to show that literally no matter how closely you look, there will always be surprises waiting to be found when it comes to fly taxonomy.


Adler P.H., Alparslan Yildirim, Onder Duzlu, John W. McCreadie, Matúš Kúdela, Atefeh Khazeni, Tatiana Brúderová, Gunther Seitz, Hiroyuki Takaoka & Yasushi Otsuka & (2014). Are black flies of the subgenus Wilhelmia (Diptera: Simuliidae) multiple species or a single geographical generalist? Insights from the macrogenome , Biological Journal of the Linnean Society, n/a-n/a. DOI:
Adler, P.H., Currie, D.C., Wood, D.M. 2004. The Black Flies (Simuliidae) of North America. Cornell University Press. Ithaca, NY & London, UK. 939 pp.

Nov 292013

On the island of Raivavae, one of the Austral Islands in the middle of the Pacific Ocean, buried deep beneath the surface of a swamp in mud accumulated at the foot of a stream for thousands of years, scientists have found all that remains of a unique new species of Black Fly (Simuliidae): larval head cases left behind when the flies molted into pupae. These subfossils, not yet hard and mineralized like conventional fossils yet still preserved in near-perfect condition by the mud, not only raise the question of how a tiny little fly found its way to an island in the middle of nowhere, but also provide the only evidence of a murder mystery 2 million years in the making.

The missing species on Raivavae is Simulium Inseliellum raivavaense, recently described by Douglas Craig of the University of Alberta and Nick Porch of Deakin University in Australia, from material collected in 2010. Despite the subfossil larval head capsules being the only “specimens”, Craig & Porch were able to determine S. I. raivavaense was a new species based on the shape, position, and number of teeth on the hypostoma, essentially the lower lip of a black fly larva’s mouth.

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Mar 102013

Dear io9,

I appreciate all the work you do to bring science news to a large and enthusiastic audience, and I’m a frequent reader myself, but as they say, with great power comes great responsibility. Unfortunately in a recent post one of your authors blew it in a big way.

In “Too many fly bites can lead to death by bug-spit poisoning”, Esther Inglis-Arkell repeatedly states that black flies inject their larvae into the bodies of the birds or people their feeding off of, and that humans are carriers of their young.

No. Just, no.

Black fly larvae are 100% aquatic, living in streams, rivers & flowing water all over the world. In some places — like northern Canada, so infamous for its black fly populations there have been songs sung about them — rivers and streams can be black with fly larvae attached to rocks and other material under the water (check out this post by Crystal Ernst to see just how many larvae can be found in the cold waters of the Great White North).

Yes, like most blood-feeding invertebrates, black flies employ anti-coagulant-laced saliva to keep the good times flowing, but there certainly aren’t fly babies in that spit. Some species of black fly in Africa and South America can transmit a nematode parasite through their saliva (Onchocerca volvulus, responsible for River Blindness, a non-fatal disease), and, as evidenced by the paper that inspired Inglis-Arkell’s post, too much fly saliva can be a bad thing, but to fear-monger that there could be fly larvae swimming in your blood isn’t cool.

Now, I recognize that Inglis-Arkell acknowledged her mistake in response to a commentor who also pointed out the error, but that acknowledgement is buried in the comments, and, unless a reader goes looking for it, will likely remain unread. Why not correct the post (preferably in a way that doesn’t hide a mistake was made) or at least add a footnote that clearly states the author’s mistake? That’s the great thing about web publishing: you can immediately clear up mistakes when they’re uncovered instead of waiting days to print a retraction or correction like in the olden days (i.e. less than 10 years ago). Your web stats show that more than 36,000 people have read articles by Ms. Inglis-Arkell today alone, meaning there are a huge number of people potentially leaving your site with a horribly inaccurate impression of black fly biology.

And that’s the real shame, because despite their bad reputation, black flies are fascinating creatures and are actually kind of cute, especially when they’re biting someone else.

Simulium sp from Ecuador Black fly Simuliidae

Simulium (Psilopelmia) bicoloratum from Ecuador (Simuliidae) feasting on my blood.

UPDATE 2013-03-10 20:30: That was fast! Less than 15 minutes after I tweeted a link to this post, io9 responded saying they were correcting their original article, and included links to those who pointed out the problem! Well done io9, well done!

Jun 282011

Ryan FleacrestThis Friday is Canada Day, and what better entomological representation of Canada than the scourge of the Great White North, the black fly! Well, I suppose grylloblattids are a better choice, but so far no one has written a song about them, so black flies will have to do! (The Grylloblattidae are a group of rare insects first discovered on a glacier in western Canada, and are the mascot of the Entomological Society of Canada)

Along with our igloos and friendship with Charlie from Thunder Bay, swarms of black flies waiting to bleed unlucky Canadians dry is one of the more common misconceptions about Canada. Luckily, most of southern Canada is relatively free of black flies, but once you get into cottage country, the woods do indeed belong to the bikojisi, as they are known to the Ojibwe. The clouds of black flies present in the back country of Northern Canada have been known to instill fear in even the most adventurous outdoorsman (or outdoorswoman), and those required to work outdoors during the spring in Boreal Canada can undoubtedly sympathize with this weeks artist, Wade Hemsworth as he sings about his experiences with black flies while working for Hydro Ontario!



Incidentally, this short film by Christopher Hinton was nominated for an Academy Award in 1992 for Best Animated Short (it lost to this entertaining cartoon unfortunately). Pretty good for an insect loathed by most Canadians eh?

Black Fly - Simuliidae - Ecuador

This black fly may be from Ecuador, but that arm is 100% Canadian!

H/T to Bug Girl for sharing this song!

This song is available on iTunes – The Blackfly Song – Folk Songs of the Canadian North Woods