When smoke gets
FOR REASONS UNKNOWN , our youth group was more enthusiastic than normal that day at summer camp on Bruny Island, taking seriously Solomon's advice to do whatever one's hand finds to do with all one's might. They had slept and snored zealously the night before. Believe it or not, they had arisen enthusiastically that morning. They had even washed their breakfast dishes with unaccustomed zest. Nobody missed a single activity that day, not even the early morning dip in the D'Entrecasteaux Channel's notoriously frigid brine. Now, at tea time, they were applying themselves diligently to the day's most important task — dinner time. The schedule said we would have a barbecue that night, so have a barbecue we did.
Being more on fire than normal, the young ones set to the task of collecting wood with gusto. It was not a high-fire danger day, so there wasn't really any likelihood of our guardian angels having to pitch in and help. In fact, they were probably enjoying themselves immensely, as the wholesome, raw fun exhibited by the campers was palpable.
Guardian angels were not the only ones hovering around in anticipation of a great barbecue. Another of God's creatures was also loitering in the wings, waiting for the fiesta to start. None of us had the slightest inkling of what was about to happen.
Now every sane creature finds smoke nettlesome, to say the least. Playing musical logs around campfires is a great Australian tradition that has evolved over the years in response to campfire smoke's diabolical habit of jibbing unpredictably, behaving like Dennis the Menace intent on creating as much disruption as possible among happily partying adults.
Master of the Unexpected
But God is the Master of the Unexpected . My fireside reverie was slowly eroded by an ever-increasing number of little black motes weaving jerkily in the smoke. At first I thought that they were specks of ash. But it slowly dawned on my Sherlock Holmesian powers of observation that they were not moving in concert with the smoke, which any self-respecting ash particles would do, but seemed to have a mind of their own. They zigged when the smoke zagged, and zagged when it zigged.
Others began to notice the strange phenomenon too. Soon the smoke was full of tiny black busybodies, hundreds of them, swarming contentedly in terpsichorean rhythm. Then something else happened. Some of the black spots, though by no means all, began to break away from the swarm and sink slowly. Soon there were dozens of them crawling across the ground and over our food-laden table. Closer inspection demonstrated clearly that these whirling dervishes were none other than — flies. Small, humpbacked flies, only a few millimeters long.
Smoke in Their Eyes
I decided to find out what I could about such bizarre creatures. Research corroborated our observation. In a surprise reversal of the norm, God has designed certain gnats that love nothing more than having their ommatidia (insect eyes) and ocelli (other insect eyes) full of smoke. They are, unsurprisingly, called smoke flies by those who are odd enough to care about such things. They belong to the genus Microsania from the family Platypezidae. They are found in cooler climates worldwide.
Like all flies, they have a larval stage, of which the common maggot of the common housefly is the best known example. Larvae of other Platypezidae that have been studied, so far as is known, eke out their grubby existence in fungi. One can reasonably safely assume that smoke fly larvae can also be found in some kind of fungus. But then again, who knows what surprise may await future investigators?
The first records of the strange predilection these flies have for noxious smoke go back to the 1920's, when workers in England and Belgium discovered them gathering in great numbers in bonfire smoke.
In North America, they were long assumed to be very rare. E.L. Kessel, of the University of San Francisco, spent years in California and Oregon searching for them using normal collecting methods of sweeping vegetation with a collecting net. He came back empty-handed every time. Having almost given up the search, he was amazed one summer's day to find them flying over the chimney of his backyard barbecue. Next day he built a huge fire of weeds and green grass. At first, only a few flies appeared, but as the day wore on, they arrived in increasing numbers until there were many hundreds of them (Evans 1968, p. 152). Contrary to traditional ideas about swarming, no mating was observed. I am now kicking myself for not being knowledgeable enough at the time of our Bruny barbecue episode to take any particular note of whether or not the flies that broke from flying formation were in pairs.
Some Interesting Features
Kessel's experiences illustrate a peculiarity of these creatures. In his classical work on flies, Harold Oldroyd put it this way (c. 1978, p. 166):
It is one of the oddities of nature that these flies, so seldom caught by the methods of ordinary collecting, can be conjured up, as it were, by the demoniacal process of lighting a fire.
This fact, combined with the observation that the only time specimens are taken by normal collecting methods is during a brief window of opportunity after a rain shower, suggests that they spend most of their time on the wing — the insect equivalent of swifts. Nobody knows if they take any sustenance while flying, and if so, what it consists of.
Nobody knows why smoke flies are attracted to the smell of wood-smoke, except in the most general sense that these flies, like many other flies from numerous families, indulge in swarming behavior. It's just that in their case, smoke, not a fence post or low bush, acts as the signal for the gathering. In most swarming fly species, swarms consist of mainly to totally male flies. Surprisingly, Kessel found that up to one third of the specimens he collected consisted of females. That's a large proportion for swarming gnats.
Fly guys who study guy flies are not sure why flies swarm. The old notion that swarming is a necessary prelude to mating is unsubstantiated by observation. The lack of mating on a large scale in swarms suggests that the bulk of matings take place immediately after fairly synchronized mass emergence of the adults from their fungal nursery.
Nobody seems to have made any attempt to find out what special structural or physiological features of smoke flies enable them to thrive in choking smoke. Do they "hold their breath" for a short time in the smoke, then have to dash out for a breather? Or have they been blessed with features that enable them to endure smoke-filled tracheae? Either way, divine intelligence had to be applied to solve the problem. The flies sure didn't figure it out for themselves.
Ogden Nash declared:
God in His wisdom
He should have read Isaiah 6:3
References and notes
Oldroyd, Harold circa 1978, The Natural History of Flies , Weidenfeld and Nicolson,
Evans, Howard E. 1968, Life on a Little-known Planet , E. P. Dutton & Co., Inc., New York
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