46 The New York ReviewFlies Like Us
Tim FlannerySuper Fly:
The Unexpected Lives of the
World’s Most Successful Insects
by Jonathan Balcombe.
Penguin, 340 pp., $18.00 (paper)We may detest flies, but our relation-
ships with them are extraordinarily
complex and often intimate. As well
as vexing us, biting us, and making
us sick, flies help feed us, remove our
waste, and control our pests. They also
consume us when we die—and many
don’t even wait that long. Some indica-
tion of the fear, awe, and loathing we
reserve for the Diptera, the insect order
in which flies are classified, can be felt
in the wonderfully onomatopoeic name
given to Satan: Beelzebub, Lord of the
Flies.
David Cronenberg’s 1986 sci- fi hor-
ror classic The Fly (a remake of the
1958 film of the same name) investi-
gates the fly- human relationship in a
thoroughly modern way. When a tele-
portation machine scrambles the genes
of scientist Seth Brundle with those of
a fly that accidentally enters the device,
Brundle (magnificently played by the
increasingly naked and bug- eyed Jeff
Goldblum) transforms before our eyes
into a fly/human hybrid. As he grows
into “Brundlefly,” he becomes enor-
mously strong and acrobatic, displaying
Olympic virtuosity on the horizontal
bars, as well as climbing vertical walls
with terrifying agility. To the wonder-
ment of his partner, Veronica Quaife
(played by the adorable Geena Davis),
he also becomes capable of feats of sex-
ual endurance that leave her in a state
of sweating, dehydrated exhaustion.
But then, to everyone’s dismay, things
start going wrong. Brundle’s body be-
gins to rot away, as does his human em-
pathy. Memorably, his feeding habits
change: he loses his teeth and begins to
eat doughnuts by vomiting copious vol-
umes of digestive fluid on them, before
slurping up the resultant mush.
If Cronenberg had had access to
Jonathan Balcombe’s extraordinary
book Super Fly, minor aspects of his
movie might well have been different.
Balcombe, a biologist of animal be-
havior who has written several books
dispelling myths about other species,
informs us that flies do not externally
digest their food in the way Brundle
does. They merely salivate on food to
moisten it, in more or less the same way
mammals do—except that we moisten
our food when it is inside our mouths.
It turns out, however, that Cronen-
berg got much of the biology right in
The Fly. (The same cannot be said of
the 1958 original, in which the scien-
tist ends up as a human head on a fly’s
body.) As Brundlefly does, flies climb
walls and cling to ceilings by extruding
a glue- like substance from their feet.
And true to the film, they also enjoy
long bouts of sex. Lovebugs of the fly
family Bibionidae are some of the most
indefatigable copulators in the animal
world, able to stay at it continuously for
fifty- six hours. Other flies indulge in
astonishing acrobatics, with males dan-
gling females upside down from their
genitals while clinging to vertical walls.
Ingenious experiments have shown
that flies really do enjoy sex. In one,
male fruit flies were paired with fe-males that were receptive to sex, while
others were paired with females that
rejected sexual advances. Both groups
of males were then given access to a
solution laced with alcohol and another
lacking it. In remarkably humanlike
fashion, the sexually frustrated males
consumed more alcohol than their sex-
ually satisfied compatriots.
A second experiment involved male
flies that were genetically engineered
so that exposure to a red light led to
ejaculation. (Human ingenuity seems
endless.) When released into a cage
with a red light at one end, the modi-
fied males crowded into the “red- light
district.” And when the flies used in
this experiment were given access to
alcohol, the sexually satisfied red- light-
district patrons drank less than their
counterparts. A healthy sex life has,
moreover, been definitively linked to
fly health. Male fruit flies that are ex-
posed to female fly pheromones but
lack an opportunity to mate become
stressed and prone to starvation, result-
ing in early deaths.
Flies are among the most diverse of
all insects, as well as the most annoy-
ing. There are 160,000 known species
of them. Biting midges and mosqui-
toes are flies, as are a myriad of other
species you’ve almost certainly never
heard of, the largest of which can hunt
small hummingbirds. Some flies drink
nectar and look like bees, while others
parasitize creatures as diverse as ants
and humans.
And they are abundant. According
to one estimate, there are 200 million
flies for every person on earth, and
their lives and body forms are so var-
ied that it’s difficult to understand why
they are all considered to belong to the
same order. But one thing they all have
in common is a single pair of wings, thesecond set (possessed by most other
insects) having become modified into
small drumstick- like projections known
as halteres, which act as flight stabiliz-
ers. The astounding agility of flies in
flight owes much to their halteres.
In The Fly, Davis’s character becomes
pregnant by Brundle and dreams that
she gives birth to an enormous maggot.
Most flies lay eggs, but some give birth
to live young. The dreaded tsetse, for
example, gives birth to a single maggot
that is three quarters the length of its
mother. Among those flies that give
birth to live maggots, Balcombe in-
forms us, “there is some urgency to...
letting them out because occasionally
the ungrateful little tykes will start eat-
ing the mother from the inside.”Even parasitic flies can become the
victims of other parasites. When the
spores of the Cordyceps fungus land
on a housefly and germinate, they turn
their victim into a fungus- serving robot.
As its body becomes riddled with fun-
gal hyphae, the fly gets an irresistible
urge to ascend to a high place. Once
there, it sticks out its feeding proboscis
and glues itself to the surface. Firmly
fixed into place, the fly then buzzes its
wings for a few minutes before locking
them into a vertical position, aiming
its abdomen upward. As the fly dies,
tendrils of the fungus push through its
skin, releasing spores to infect other
flies and begin the cycle anew.
Scuttle flies specialize in parasitiz-
ing ants, and some have a particularly
gruesome modus operandi. The flies
stalk their victims along ant trails, and
when they find a vulnerable ant they
lay a single egg on its thorax. When
the egg hatches, the maggot enters
the ant through the fissure betweenits head and thorax. From there, the
maggot burrows into the ant’s head,
where it feeds on powerful biting mus-
cles. “After a couple of weeks,” Bal-
combe writes, “the full- grown maggot
releases an enzyme that dissolves the
membrane connecting the ant’s head to
its body.” As the headless body stum-
bles around, the maggot turns the ant’s
head into a protective capsule from
which the adult fly emerges two weeks
later. (I’m grateful that the makers of
The Fly did not have access to Super
Fly, if only because I could not bear the
sight of Davis’s head rolling around on
the floor of Brundle’s apartment.)
Botflies are large flies that parasitize
mammals. Their eggs are sometimes
carried by mosquitoes, which spares
the large adult fly risk of death from a
swatting tail or hand. They are common
parasites on reindeer, cattle, and even
dogs. Some, known as snot bots, squirt
larvae into the nostrils of sheep, goats,
deer, moose, horses, and camels, from
which they migrate to the sinuses, ma-
ture, and get snorted out to pupate in
the earth. The only known example of
the species called the mammoth botfly
was found fossilized in the stomach of
a frozen mammoth. Before it vanished,
along with the last of the mammoths
over four thousand years ago, it presum-
ably irritated their trunks and throats.
One species of botfly thrives today
because its preferred host, humans,
exists in unprecedented numbers. As
Balcombe writes, in 1999 the life cycle
of the human botfly was investigated
in detail, albeit inadvertently, by Rob-
ert Voss of the American Museum of
Natural History. He encountered the
species in French Guiana while hik-
ing shirtless through the rain forest.
When back home in New Jersey he no-
ticed slight prickling sensations on his
back, and his wife, Nancy Simmons,
saw red lumps that resembled irritated
mosquito bites. Voss eventually sought
the services of a dermatologist, who
referred him to a “tropical specialist”
Balcombe calls Dr. X.
Dr. X was eager to see Voss, exclaim-
ing, “I think you have myiasis,” a para-
sitic infestation by a fly larva. “Ah yes,
here it is!” he cried as he operated be-
hind Voss’s back. Without explaining
what he was doing, he cut out a conical
hunk of bloody flesh that had a small fly
larva wriggling at its apex. Voss had not
given permission for the excision, and
he suspected that Dr. X desperately
wanted a specimen for his collection.
When Dr. X moved to excise a second
maggot, Voss objected, and when he
asked for the excised maggot to be re-
turned to him, Dr. X “squawked with
indignation.” Finally, Dr. X offered to
waive his fee in exchange for the first
maggot. Voss still regrets that he ac-
cepted the offer.
Voss and Simmons started a “botfly
watch,” and a bond began to develop
between Voss and his sole surviving
maggot. Hosting the maggot was obvi-
ously a deeply moving experience for
Voss, who remarked to Simmons that
it “was as close to pregnancy” as he’d
ever get. When the larva and its pupal
case emerged from Voss’s body, he put
it in a safe place; when the adult fly
hatched five weeks later, it and its pu-
parium were donated to the collections‘Head of a Drone Fly’; engraving from Robert Hooke’s Micrographia, or, Some
Physiological Descriptions of Minute Bodies Made by Magnifying Glasses, 1665Natural History Museum, London /Bridgeman ImagesFlannery 46 47 .indd 46 11 / 16 / 21 5 : 52 PM