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Warwick Kerr: Creator of Killer Bees or Better Bees?

November 2018 1
The man who “created killer
bees” died a few weeks ago.
For decades, he was disparaged
in newspapers, magazines, and even
books, for creating Africanized honey
bees (AHB) after bringing African
stock to Brazil. By some accounts, it
sounded as if he had unleashed the
fifth apocalyptic horseman.
For the importation of Africanized
stock and its subsequent release, Dr.
Warwick Kerr has been described as
malicious, or, more benevolently, as
an inept scientist. Others saw him
differently. To many in Brazil, he was
a hero who ushered in an era of ge-
netic research. When he died on Sat-
urday, September 15, Brazil went into
mourning. Flags were lowered to
half-mast. The Amazon river city of
Manaus began three days of official
mourning – upon the death of a bee
scientist! Kerr was a beekeeper, re-
search scientist, geneticist, educator,
and political activist. The mayor of
Manaus declared the three-day trib-
ute so the city’s two million residents
could honor the man who improved
the welfare of the people of the rain-
forest– and all of Brazil.
Few scientists have been described
from more divergent viewpoints. Did
he create a disaster? Or did he aid
beekeepers in the Americas? With his
recent death, six days past his 96th
birthday, we will try to unravel the
truth about Professor Kerr and look
at his legacy – especially the fallout of
his “killer bees.” To try to understand
the dichotomy of opinion, I spoke
with Kerr’s grandchildren, as well as
people intimate with honey bees in
Africa, California, and Arizona.
If you are familiar with the name
Warwick Kerr, you likely know that
he brought Africanized genetic stock
from southern Africa to Brazil in 1956
to replace the European bees, which
fared poorly in the tropics. His breed-
ing work created a hybrid bee. Since
the introduction of this new strain of
bees, Brazil’s annual honey produc-
tion increased from 15 million to 110
million pounds1 and crop pollination
improved. Beekeepers would eventu-
ally triple their honey crops – from 40
to 120 pounds per hive. But it was a
disruptive change.
Those who knew him, described
Dr. Kerr not only as a beekeeper, and
careful geneticist, who took his role
of educator seriously, but also as an
uncompromising humanitarian. His
granddaughter Priscilla recalled that
on Sunday mornings, he would lead
her and other children into the fave-
las, or slums, of the city to read from
the Bible and deliver food. In the
1960s, when Brazil was controlled
by a military dictatorship, his activi-
ties landed him in prison twice. We
will get to the circumstances, but to
understand them, we have to know
Warwick Kerr’s roots.
Kerr was born into a middle-class
family in 1922 near São Paulo, Brazil.
Some of his Scottish ancestors had set-
tled in the southern USA, then moved
to Brazil at the end of the American
Civil War. At university, he earned an
agricultural engineering degree. He
specialized in genetics and pursued
post-doctoral studies in the United
States. One of his supervisors was
the famous geneticist Theodosius
Dobzhansky, a pioneer of modern
genetics. With Dobzhansky, Kerr re-
searched fruit flies (Drosophila), the ‘go
to’ bug for genetic studies. Their 1954
fruit fly research resulted in one of
the first publications using statistical
genetics. Then Kerr returned to Brazil
and his interest shifted back to bees.
Castes among stingless Bees
Kerr spent years researching bees
in the Brazilian rainforest. Some of
Brazil’s poor people were indigenous
honey gatherers, or meleiros, who
were named for their Melipona honey
trees. There were only 7,000 meleiro
people and their precarious hunter-
gatherer existence in the 1940s con-
cerned Dr. Kerr. He hoped that his
studies would draw attention to the
importance of preserving the Melipo-
na bees, the Melipona honey trees, and
the people who lived off those bees.
Warwick Kerr
Creator of
Killer Bees
or Better Bees?
by ron MiKsha
Dr. Warwick Kerr in his garden with his
granddaughter, Dr. Priscilla Kerr Hatae
American Bee Journal2
From Kerr’s 1950 Melipona caste paper
Understand and help the Melipona
bees, and you help the meleiro peo-
ple, Kerr figured. In turn, the meleiros
helped Kerr. As a young researcher
in his twenties, they led him to elu-
sive bee trees and showed him which
flowers their bees used for forage.
One species which Kerr studied,
Melipona quadrifasciata, is a eusocial
stingless bee, native to southeastern
coastal Brazil. The indigenous me-
leiros call it Mandaçaia, which means
“beautiful guard,” as there are always
guard bees defending the narrow en-
trance of their colony. An example
can be seen in the header image, pho-
tographed by ecologist Elinor Lich-
tenberg in 2006. Melipona build mud
hives inside hollow trees. These have
narrow passages allowing just one
bee to pass at a time. Although they
are stingless, they can give a nasty
Kerr's research resulted in “Genetic
Determination of Castes in Melipona”
which explained the development of
drones, queens, and workers among
Melipona. Kerr found that their caste
development was different from
honey bees (Apis mellifera). Drones in
both species are haploid, but with Me-
lipona, things get complicated for the
girls. Kerr explains:
In Apis mellifera, “a larva develops
into a queen or into a worker depend-
ing upon the food it receives. In Meli-
pona, on the other hand, caste deter-
mination is genotypic. Fertile females
(queens) are heterozygous in some
species for two, and in other species
for three, pairs of genes, homozygosis
for any one of which makes the indi-
vidual develop into a worker.” – Kerr,
For Melipona, inherited gene com-
binations determine caste. Females
have two sets of each gene, one from
each parent. Genes contain variants,
called alleles (A or a; B or b). Combi-
nations of these in caste-determining
genes determine whether a queen or
worker develops. If they are made of
two different alleles (Aa and Bb), the
female will be a queen; if either set
is identical (AA or BB), she will be a
worker– see the table below. For hon-
ey bees, it’s nutrition; for these sting-
less bees, allele combinations make
the difference.2
If you find this confusing, imagine
sorting it out with 1940s technology,
as Kerr did. At the time, DNA had not
even been discovered. Kerr couldn’t
peek beneath the hood to identify the
actual alleles. He solved the mystery
with back-crosses, observations, and
statistics. Publications in the presti-
gious Science and Proceedings of the
American National Academy of Sciences
followed. His work was considered
so significant that he was one of the
first foreign scientists elected to the
US National Academy of Sciences.
He was also one of the youngest. This
was just the start. Kerr’s research led
to 622 published research papers dur-
ing his 60-year career.
Creation of the afriCan honey Bees
While working in the rainforests,
Kerr developed a sympathy for the
poverty-stricken aboriginal hunt-
ers and farmers who supplemented
their diets with honey from native
stingless bees. He saw other farmers
struggle to pollinate their crops and
produce honey with imported Euro-
pean honey bees. European strains
were poorly adapted to the tropics. A
few farmers and monks kept the lan-
guid bees, mostly to collect beeswax
for church candles. Kerr felt that an
infusion of tropical genetics would
create a rugged hybrid and improve
the European honey bees.
In 1956, Kerr went to Africa and
assessed prolific honey producers.
Using their progeny at his lab, he be-
gan creating hybrids suited to Brazil.
Reportedly, a technician mistakenly
removed queen excluders from the
breeding hives, allowing some of the
26 imported African queens to escape
with swarms. Others have claimed
that Kerr’s lab distributed queen cells
reared from the stock and shared
them across Brazil. The latter doesn’t
seem likely as the occurrence of the
new AHB radiated from a single
spot at his Rio Claro field lab and not
from a series of ‘hot spots’ appearing
simultaneously across the country.
From their initial appearance, the
population spread in growing con-
centric rings around the lab, advanc-
ing 300 miles each year. There was no
way to put them back in the box once
they escaped into the rainforest.
It seemed like an unmitigated di-
saster. The bees were difficult to man-
age. They stung a lot. Some Brazilian
beekeepers gave up beekeeping. Hive
counts declined. That would change,
but it would take a decade. Mean-
while, Brazil was ruled by a military
dictatorship, which Kerr vocally op-
posed. He was imprisoned in 1964 for
criticizing government corruption.
In 1969 he was again arrested, this
time for protesting that Brazilian sol-
diers, who had raped and tortured a
nun, went unpunished.3 The military
could neither kill Dr. Kerr, nor keep
him imprisoned for long, because of
his international acclaim. Instead, the
Brazilian government set about de-
stroying Kerr’s reputation, claiming
that he had created assassin bees. The
press ran with the story.
Honey bees with African genes are
more aggressive than European bees.
Beekeepers in Brazil had to learn new
management skills. Although the
venom is the same, more bees attack
if their colony is disturbed. People
have died from massive stings. Some
of the traits which make Africanized
bees exceptional pollinators (refined
olfactory sense, quicker movements,
flights in inclement weather, supe-
rior navigation skills) also make them
more likely to sting en masse. In time,
Brazilian farmers learned to manage
them more safely. After the African
bees completely colonized the coun-
try, Brazil’s status as a honey produc-
er went from 43rd in the world to 7th.
Partly due to superior pollination,
Brazil also became a major agricul-
tural producer.
In 1991, Bob Miese, an American
keeping bees in Brazil, produced
the film, “The Workable Africanized
Bee” to expose what he described as
misconceptions about AHB. To build
up his Brazilian business, Miese col-
lected feral swarms, fitting wedges
of brood into conventional frames
and shaking the associated bees into
new hives. He collected AHB from
bushes and cavities, placed them in
Langstroth hives, and trucked them
November 2018 3
to melon pollination.
“I’ve heard American scientists
say that the Africanized bees don’t
produce honey. That is wrong. They
produce lots of honey.” Indeed,
200-pound crops became common.
AHB kept Bob Miese in business as
a honey-producer and pollinator. In
his film, AHB are noticeably jumpy,
but he and his crew generally worked
without gloves, and often wore
shorts. “The Africanized bee can be
selected to reduce aggressiveness,
just like you would do with Italians,”
said Miese.
AHB, the hybrid which Dr. Kerr
created, helped turn his impover-
ished homeland of Brazil from a back-
water of food production into one of
the most prolific honey and agricul-
ture countries in the world. In 1994,
L.A. Times headlined: “Brazil’s honey
production has soared since the ornery in-
vaders took over beekeepers’ hives.”4 But
there remained the inescapable fact
that people were being stung – and
killed – by those same bees.
Killer Bees: how far Can they go?
The dictatorship discredited Kerr
and the North American press sensa-
tionalized the Brazilian press releases.
In fact, assassin bees, or “killer bees”
as they became known, were danger-
ous. Most attacks occurred at the edge
of AHB’s northward advance.
Some of the tragedies were due to
lack of caution by people unprepared
for the sudden appearance of highly
defensive bees. The worst attacks
usually occurred when AHB arrived
in new territory. Afterwards, the
temperament of the bees, according
to beekeepers on the scene, cooled –
though not to the same level as the old
European stock they replaced. Some
have speculated that this was due
to an F1-hybrid effect. Upon arrival,
some European-Africanized cross-
ing occurs, making a more vigorous
offspring. With time, African genes
dominate over the heterotic hybrid
and the bees become milder. I have
not seen research on this speculation.
Studies of genetics immediately after
arrival, compared to AHB a few years
later, are rare.
Femilarani Antomagesh, a biology
graduate student at the University of
Calgary, told me that people in her
Kenyan homeland don’t worry about
bee attacks. She showed me photo-
graphs of the original African bees,
landing on a spoon as she offered a bit
of honey. “Kenyans,” she said, “know
that bees are important for pollina-
tion.” Beekeepers in Africa know that
their bees can be defensive at times,
but they are not called ‘killers’ and fa-
tal stings are rare. This concurs with
suggestions that after the initial wave
of hybrid bees, AHB behaves more
like bees in Africa.
Venezuela provides an example of
this effect. AHB reached Venezuela
in 1975. Three years later, they had
fully colonized the country. That year,
about 100 people were killed. But in
1990, there were 12 fatalities.5 It is
unlikely that the sharp decline was
entirely due to human caution and
education. The milder temperament
of AHB reported by beekeepers prob-
ably played a role.
Nevertheless, Africanized stock
are often called killer bees. The name
arose in 1964. It is probably not a co-
incidence that this was the year that
Kerr went to prison for criticizing
the government. By 1973, the term
“killer bees” was in broad use, clut-
tering more and more ink until 1999
when usage began to fade. The fear of
AHB was also subsiding. Today, the
expression killer bees is less common
in magazines and newspapers than it
was 25 years ago.6
Killer bees were once regular fea-
tures in popular culture, sometimes
earning top billing in thrillers such as
Killer Bees (1974), The Swarm (1978),
Deadly Invasion (1995), and Killer Bees
(2002). The best known of the lot, The
Swarm, based on Arthur Herzog’s
book, is remembered today because
it tops lists of the worst movies ever
made.7 Sometimes killer bees ap-
peared for laughs. Forty years after
African stock was released in Brazil,
Homer Simpson tells Marge not to
worry about their missed flight to
the sunbelt. “It’s okay, Marge,” said
Homer, “We don’t need to go on a
trip. We’ll just wait for the killer bees
to come to us.”8 Twenty-five years
later, Homer is still waiting.
That’s not the way it was supposed
to be. Predictions made in the 1980s
suggested that the Africanized stock
should have been terrorizing people
as far north as Virginia and Oregon
by 1997. It was a reasonable forecast,
albeit wildly incorrect. AHB reached
Texas in 1990. If it migrated at its pre-
dicted pace (300 miles per year), it
would soon be endemic in all warmer
parts of North America. But an odd
thing happened. The northward ex-
pansion slowed. In 2018, AHB was
twenty years behind its expected lo-
How far will the Africanized bees
go? It seems mostly dependent on
climate. AHB does not winter well.
In a 1982 American Bee Journal article,
reprinted as the next article in this is-
sue, Warwick Kerr himself thought
that the general demarcation would
be about 34 degrees latitude – north
and south.9 It’s notable that 60 years
since appearing next door in Brazil,
AHB is still absent in temperate Ar-
gentina. Climate clearly provides a
The Legacy of Warwick Kerr’s Bees
Kerr’s Africanized stock is now
a permanent fixture of much of the
Americas’ ecology. Where these bees
have settled, 98% of feral colonies
are AHB with about twelve swarms
per square mile.10 Besides being bet-
ter tropical honey producers and pol-
linators, Africanized colonies don’t
succumb to varroa. Mite medications
are not used on AHB in Brazil. Afri-
canized workers and queens spend
less time than their European counter-
parts developing in their cells. Since
mites only reproduce while hidden
in capped brood cells, the mites don’t
have as many offspring as when cou-
pled with slower-developing Europe-
an pupae. Today, much of the world’s
organic honey is produced by African-
ized honey bees in Brazil’s forests. The
honey is doubly organic – produced
in areas untouched by pesticides and
produced in unmedicated hives.
Africanized stock is now preferred
by some beekeepers in the United
States where its resistance to varroa
and its superior honey production
has made it a favorite. I spoke to Cali-
fornia beekeeper Susan Rudnicki. “I
won’t keep any other type of honey
bee,” she told me. Rudnicki has kept
bees for nine years and has 30 colo-
nies. Some sit on large estates in Bev-
erly Hills. All are fully Africanized.
She agrees that they are more ani-
mated than European stock. “You lift
Susan Rudnicki operates chemical-free
Africanized stock on foundationless
American Bee Journal4
the lid on an Italian and the bees just
sit there. My African bees are more
lively, moving around on the top bars
and sometimes flying up at me. But
in nine years, I’ve only had two colo-
nies which were too temperamental
to keep in a backyard. I gave them to
a friend who keeps a hundred AHB
hives on the edge of a big avocado
She laments that ten years ago a re-
search scientist spoke to a nearby bee
club, claiming that Africanized bees
are so ferocious that they will smash
into a veil and spray venom onto a
beekeeper’s face. That story scared a
lot of beekeepers. I don’t know if it
actually happened to anyone. It’s cer-
tainly not been Rudnicki’s experience.
Susan Rudnicki started with Afri-
canized stock when she began bee-
keeping. An enthusiastic organic gar-
dener, she said that she didn’t want
to have bees that needed miticides
to stay alive. With her biology back-
ground, it made sense to her that un-
treated bees (“survivor stock”) would
have some resistance to pests. Rud-
nicki has seen the occasional phoretic
mite, but they are rare in her hives.
She prefers Africanized stock for their
hardiness and honey production, but
particularly because they survive
without mite treatments.
Meanwhile, my niece, keeping
bees in Arizona, is not so enthralled.
I asked Monica King if she liked AHB.
“Not so much,” she told me. My niece
grew up rearing queens and extract-
ing honey with her father, my brother
David Miksa.
She remembers the gentle stock her
father still breeds in central Florida.
“Beekeeping with Africanized stock
isn’t much fun,” she said. “They are
too unpredictable.” She described a
recent bee rescue. This summer, at a
residence near Tucson, she collected
feral AHB bees on comb while the
homeowner and his family huddled
around her. No one was stung. But
two weeks after the bees were relo-
cated, they became explosive. She
requeened the hive with a European
queen and their manners quickly im-
proved. Her preference is to continue
requeening Africanized stock and
that’s what she teaches beekeepers
whom she mentors.
the real warwiCK Kerr
Warwick Kerr’s seven children
became physicians and professors.
His grandchildren remember hikes
through gardens where he taught
them the Latin names of flowers and
explained how bees visited each type
of blossom. He loved teaching and
was described as spellbinding and
charismatic. He was also described
as a bit formal, not one to hug or ex-
press feelings openly – though he had
a good sense of humour.
His students respected his enthusi-
asm and energy (he worked 70-hour
weeks) and he was keenly interested
in their success. But he did not suffer
fools. He would explain something
once, maybe twice, but then you had
better go away and come back prop-
erly prepared.
Kerr’s academic and civic accom-
plishments were formidable. He was
largely responsible for establishing
the study of genetics in Brazil. He
was a director of the National Insti-
tute for Research in the Amazon. At
the University of São Paulo, he estab-
lished the Department of Genetics,
which focuses on entomological and
human genetics, using mathematical
biology and biostatistics. Later, at the
Universidade Estadual do Maranhão,
he created the Department of Biology
and served as Dean of the University.
Kerr had memberships in the Brazil-
ian Academy of Sciences, the Third
World Academy of Science, and the
US National Academy of Sciences.
I became interested in Warwick
Kerr’s story decades ago. Like most
people, I thought he made a mistake
bringing queens from Africa. Then I
investigated his motivation and read
several of his genetics papers. Finally,
I saw the significant positive impact
AHB had on Brazil’s agriculture. I re-
alized his genius and his fearless ded-
ication to the welfare of Brazil’s poor-
est people. Partly due to his influence,
the meleiro people still live on their
tribal lands in southeast Brazil.
Were his Africanized hybrid bees
a tragic failure? The people of Brazil,
Monica King, inspecting a colony which
started as an AHB rescue hive. She re-
queened it with a European queen.
Warwick Kerr, center, at his Ribeirão Pre-
to lab in 1968
Warwick Kerr and family on his 95th birthday, 2017.
November 2018 5
who lowered their flags in his honor,
don’t think so.
1 Food and Agriculture Organization of the
United Nations retrieved from www.fao.
org September 20, 2018.
2 Kerr, Warwick, 1950. “Genetic Determi-
nation of Castes in Melipona”, Genetics
35:143 pp 143-151.
3 Coelho, Marco Antônio, “Warwick Kerr: a
Amazônia, os índios e as abelhas”, 2005.
Estudos Avançados 19 (53), pp 51-69.
4 Margolis, Mac, 1994. “’Killer’ Bees Make
Honey of a Deal With Brazil : Produc-
tion has soared since the ornery invaders
took over beekeepers’ hives”. Los Angeles
Times, April 5, 1994.
5 Winston, Mark, 1992. “The Biology and
Management of Africanized Honey
Bees”, Annual Review of Entomology
1992.37 pp 173-193.
6 Google N-gram: retrieved September 20,
7 The Sunday Times described The Swarm as
“simply the worst film ever made” via
The Guardian, April 26, 2001.
8 The Simpsons, “Fear of Flying” Season 6,
Episode 11, December 18, 1994.
9 Kerr, Warwick, S. de Leon del Rio, M.D.
Barrionuevo. 1982. “The Southern lim-
its of the distribution of the Africanized
honey bee in South America”, American
Bee Journal 122: 196-98.
10 Rangel, Juliana, et al., 2016. “Africaniza-
tion of a feral honey bee (Apis mellifera)
population in South Texas: does a decade
make a difference?” Ecology and Evolu-
tion, 6(7):2158–2169.
Ron Miksha, a hobby
beekeeper, is currently
engaged in bee ecology
research at the Univer-
sity of Calgary. Ron was
a commercial honey
producer and queen
breeder with farms in
Florida, Saskatchewan,
and Alberta. He lives
in Calgary with his family which includes a
recent addition - Misty, the Wonder Dog. Ron
can be reached via
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
The arrival to the United States of the Africanized honey bee, a hybrid between European subspecies and the African subspecies Apis mellifera scutellata, is a remarkable model for the study of biological invasions. This immigration has created an opportunity to study the dynamics of secondary contact of honey bee subspecies from African and European lineages in a feral population in South Texas. An 11-year survey of this population (1991–2001) showed that mitochondrial haplotype frequencies changed drastically over time from a resident population of eastern and western European maternal ancestry, to a population dominated by the African haplotype. A subsequent study of the nuclear genome showed that the Africanization process included bidirectional gene flow between European and Africanized honey bees, giving rise to a new panmictic mixture of A. m. scutellata- and European-derived genes. In this study, we examined gene flow patterns in the same population 23 years after the first hybridization event occurred. We found 28 active colonies inhabiting 92 tree cavities surveyed in a 5.14 km2 area, resulting in a colony density of 5.4 colonies/km2. Of these 28 colonies, 25 were of A. m. scutellata maternal ancestry, and three were of western European maternal ancestry. No colonies of eastern European maternal ancestry were detected, although they were present in the earlier samples. Nuclear DNA revealed little change in the introgression of A. m. scutellata-derived genes into the population compared to previous surveys. Our results suggest this feral population remains an admixed swarm with continued low levels of European ancestry and a greater presence of African-derived mitochondrial genetic composition.
  • Marco Coelho
  • Antônio
Coelho, Marco Antônio, "Warwick Kerr: a Amazônia, os índios e as abelhas", 2005. Estudos Avançados 19 (53), pp 51-69.
Killer' Bees Make Honey of a Deal With Brazil : Production has soared since the ornery invaders took over beekeepers' hives
  • Mac Margolis
Margolis, Mac, 1994. "'Killer' Bees Make Honey of a Deal With Brazil : Production has soared since the ornery invaders took over beekeepers' hives". Los Angeles Times, April 5, 1994.
The Southern limits of the distribution of the Africanized honey bee in South America
  • Warwick Kerr
  • S De Leon Del Rio
  • M D Barrionuevo
Kerr, Warwick, S. de Leon del Rio, M.D. Barrionuevo. 1982. "The Southern limits of the distribution of the Africanized honey bee in South America", American Bee Journal 122: 196-98.