The New York Review of Books - USA (2021-12-16)

46 The New York Review

Flies Like Us

Tim Flannery

Super 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, the

second 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 between

its 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, 1665

Natural H

istory Museum, London /Br

idgeman Images

Flannery 46 47 .indd 46 11 / 16 / 21 5 : 52 PM