17 August 2019 | New Scientist | 39S
TEPPING out of his house to survey the
destruction, Hermes Conde felt like he
had been transported to another world.
“It was as if an atomic bomb had hit. Nothing
was standing,” he says. “I couldn’t recognise
the landscape around my own home.” It was
21 September 2017 and Hurricane Maria had
just torn Puerto Rico to shreds.
An estimated 2975 people died in the
worst natural disaster the Caribbean island
has ever witnessed. From the early hours of
20 September through to mid-afternoon the
next day, Maria bisected Puerto Rico like a
100-kilometre-wide buzz saw. It plucked up
trees and hurled roofs from homes like
Some people have died in such attacks, not
because the bees’ venom is particularly
potent, but due to the sheer number of stings.
Hollywood cashed in on people’s fears with
a string of horrifying bee movies. Films like
The Swarm, Killer Bees and Deadly Invasion:
The killer bee nightmare mythologised the
insects, which began to spread across the
southern US in the 1990s. By this time, “killer”
bees had taken root in 20 countries on two
continents. Then, at the height of their infamy,
a queen stowed away aboard a ship in Texas.
She was bound for Puerto Rico.
Hybrid bees were first recorded on the
eastern side of the island in 1994. From the
start, they were just as quick to interbreed with
local bees as they had been on the mainland –
and just as aggressive. Records reveal four
deaths, including a 2-year-old boy, in the first
three years. The authorities were quick to
respond. Emergency calls resulted in fire
services spraying more than 2000 hives
with a soapy solution that asphyxiated
the inhabitants. Then, in September 1998,
Hurricane Georges hit the island, sending
bee numbers plummeting.
It was during the post-Georges recovery
that Tugrul Giray at the University of Puerto
Rico got involved. He was keen to compare the
island’s bees with those in Hawaii, which are of
purely European origin. “The weird thing is thatwe were going up these trees expecting some
kind of a fight on our hands,” he says. “We
wanted to collect the baddest bees. But they
were really just as sweet as can be.” This wasn’t
the exception – Giray kept finding hive after
docile hive everywhere he looked. Wondering
whether the insects might be remnants of the
island’s European bees, he decided to carry out
some genetic tests. “Even the nicest colonies
turned out to be of mixed African and European
descent,” he says. “It was a total surprise.”
It took a few years, but bee numbers
eventually rebounded to their pre-Georges
levels. Bee attacks, however, did not: these
had dropped from 10,000 a year to 600. Giray’s
bafflement grew. “We tried to scientifically >“ By the 1990s,
killer bees had
taken root in
20 countries on
two continents”
Frisbees. The pounding rain sent flash floods,
metres deep, rushing into populated areas.
Downed trees and power lines blocked the
roads. Electricity and water supplies were
cut off for months after the storm.
Conde’s first priority was to get petrol for his
generator. It would take him 23 hours on foot,
but fuel wasn’t the only thing he was looking
for. Conde is a beekeeper and along the way
he tapped into a network of fellow apiarists
trying to discover the fate of their insects.
The situation looked bleak. Hurricane Maria
had almost annihilated Puerto Rico’s bees, but
Conde was determined to rescue the survivors.
It may sound like a strange mission in the
middle of such chaos, but these are no ordinary
bees. They are among the most incredible
insects in modern evolutionary history. In just
a decade, they have mysteriously transformed
from killers to docile honey makers. They
may even hold secrets that will help us
breed disease-resistant bees in the future.
Their story begins in Brazil, in 1956,
with a local geneticist called Warwick Kerr.
Honeybees aren’t native to the Americas, and
at that time South American nations relied on
imported European bees, Apis mellifera. The
tropical heat, however, made them sluggish.
Monks kept them to provide beeswax for
church candles, but European bees were
becoming increasingly unable to meet the
Brazil’s demands for honey and crop
pollination. So Kerr travelled to Tanzania
to acquire some East African lowland bee
queens for a breeding programme. This
subspecies, Apis mellifera scutellata, is
notoriously aggressive, but he hoped that by
crossing them with their European cousins
he could create a hybrid with the docility
and honey yield of the European bee and
the resistance to disease and heat of the
African one. It would just take a little time.
He hadn’t planned for his prototypes to
escape, but that is exactly what happened the
following year. Fleeing into the rainforest, the
hybrids interbred with local honeybees, soon
becoming dominant, first in Brazil then across
the Americas. News of the bees’ advance was
intermingled with tales of their legendary
aggression. The truth didn’t need much
embellishment. When European bees are
provoked, about 10 per cent of hive members
will attack, but these hybrid bees often retaliate
en masse, emptying the hive in swarms of up
to 800,000 individuals. They will give chase
for up to half a kilometre and are content to
wait it out if their target attempts to hide
underwater, continuing the barrage of
stings when the victim resurfaces for air.After just a decade
on Puerto Rico,
killer bees like
this had lost their
famed aggression