The Killer Bee – How and why did they spread over America?

From the ’60s, American media picked up a situation that shook up countries all around the world: hybridization of two kinds of honeybee gave rise to a competitive, unstoppable and deadly brand new organism. The killer bee had came. This small insect emerged on the front cover of numerous renowned magazines and papers during quite a long time and it even supposed that the main role in some horror movies. However, when did fiction transcend reality? What is true in this particular story? Continue reading to get the replies.

The killer bee

The origin of killer bees
The most famous honeybees belong to the species Apis mellifera, which is widely spread all around the world. Each of its subspecies are native to Europe, Africa and Asia, although a number of them (specially the European ones) happen to be subscribed to different countries globally due to their significance for crop pollination and honey production.

The breeding of honeybees
The breeding of honeybees (beekeeping or apiculture) is a prevalent practice all over the world. In America, European honeybees were imported for this purpose.

The Source of killer bees underlies about the subspecies A. mellifera Scutellata or African honeybee, indigenous to Sub-Saharan Africa and southeast of Africa. Unlike European honeybees, these are extremely competitive. In America, these bees hybridized with sterile European or Western honeybees, giving rise to hybrid bees known as Africanised bees. These hybrids, along with native African honeybees and the descendants they gave birth in America, were colloquially termed as killer bees.

How and why did they spread over America?
In The ’50, the importation of European honeybees to America was a regular practise. But while beekeeping had good results in the USA, it did not seem to function in South America since honeybees from Europe didn’t adapted nicely to tropical climate. Thus, in 1956, the Brazilian scientist Warwick Kerr suggested to export African honeybees into Brazil rather than the European ones in an effort to improve honey production. Then, the unique main difficulty he had to solve was the competitive character of the subspecies. The most important objective of Dr. Kerr was going to acquire a docile variety of bees which was also effective in tropical climates with artificial selection and cross-breeding of the African honey bee (A. m. scutellata) using different European honeybees.

killer bee spreading

The undertaking would was a victory if it were not for the fact that a number of swarms inadvertently escaped quarantine. The experimental bees immediately shaped new colonies and started to hybridize with both domestic and wild European honeybees, giving rise to the Africanised honeybees that were more competitive and less effective than Dr. Kerr anticipated.

These bees are currently located in nearly all around the American continent. In the USA, they didn’t spread further north due to their tropical origins, so their selection of distribution within North America is restricted to the southern countries of the USA.

The spread of the killer bee over America was quickly, even hitting the southern countries of the USA in a few decades since they escaped.

Analysing the killer bee

In the start, beekeepers confronted the hard to distinguish the African honeybees from the European ones, since they seem very similar at first glance. But, exhaustive studies allowed to confirm the presence of, at least, two differences between them: both African and Africanised honeybees are slightly bigger (roughly 10%) and darker than the European ones. Bad news is that it is still crucial to utilize morphometric analysis to differentiate them properly, particularly if African genes are more diluted.

African honeybee and European subspecies of honeybees
To the left, Apis mellifera scutellata or African honeybee; to the right, Apis mellifera or one of the European subspecies of honeybees.

In the start, beekeepers confronted the hard to distinguish the African honeybees from the European ones, since they seem very similar at first glance. But, exhaustive studies allowed to confirm the presence of,

African honeybees reveal some behavioural traits that make them potentially more harmful than their European relatives:

  1. They are more competitive. It is implied that being subjected to different environmental pressures within their native habitats could be the main cause of the gap of aggressiveness between these honeybee subspecies: traditionally in Europe, beekeepers have selected less competitive and manageable varieties, while in Africa it’s more usual to accumulate wild honeycombs (a clinic colloquially known as ‘honey hunting’). The two ‘honey hunting’ and a significant presence of natural enemies might have been lead into the selection of African varieties’ increased defensiveness compared to that of European subspecies.
  2. They reach massive attacks. Unlike European honeybees, which assault in groups of 10-20 people, African honeybees can do it in groups of 100-1000 people. There exist evidences of this emission of pheromones that could induce other bees to hugely combine the assault. Moreover, the defended area around the nest is greater and the degree of stimulation required to activate an attack is significantly lower than in the European honeybees.
  3. Honeybee colonies normally spanned 1 to 3 times a year (i.e. when the colony becomes too big and resources are plentiful, a new queen is reared along with the hive divides), while African honeybee hives could split up to 10 times annually, even more if they feel threatened.
  4. Selection of nesting site. Because African honey bees swarm more often, fewer individuals are involved in each swarm, so they don’t demand a massive cavity to construct a nest. They’re also less discerning than their European relatives, so they can be found inside pipes, trash cans, building cracks, holes in the ground, etc..
  5. This is possibly the most curious behavioural trait of African honeybees. First of all, a small African American swarm containing a queen lands on a European colony. As time passes, the worker bees at the African swarm begin to swap food and pheromones together with the European workers from the colony. This gradually ensures that the adoption of the African bees to the European colony. Somewhere in this procedure, the European queen vanishes (likely murdered by the African bees) and the African queen has been introduced to the colony. By this process, European bees are eventually substituted by African bees as well as their hybrid descendants.
Honey bee attack
Texas man survives 1,200 bee stings
Honey bee colonies
Honey bee colonies


Though reproductive biology and development Are Extremely similar One of honeybee races, African honeybees show some biological traits that Give them adaptive advantages with Regard the European ones:

1. Greater generation of drones (male bees) by parthenogenesis. African colonies produce proportionally more male bees than European honeybees, which gather during the nuptial flight forming cloud of hundreds of individuals. Thus, the probability that a European queen mates with the African American increases, and therefore the probability to perpetuate African genes.
2. Speedy improvement. African colonies grow and spread faster than the European ones.
3. Greater resistance to pathogens and parasites. By way of instance, to Varroa destructor, to the tiny hive beetle Aethina tumida or even to bacteria of the genus Paenabacilis, that have finished with a great deal of European honeybee populations in America.

The way all these traits state on hybrid bees fluctuates dependent on the proportion of African and European genes they present, which depends at precisely the same time on the space to the original spreading focus. Therefore, the hybrid bees from the USA tend to be genetically closer to European honeybees and thus are less competitive than the Africanised honeybees from different sections of America.

Are they a public health concern?
The amount of stings received by their victims (causing anaphylactic reactions even in non-allergic people), the aggressiveness of the attacks, their flexibility to select a nesting site (favouring their existence in urban areas) and their sensibility against any vibration or noise, are reasons enough to consider both African and Africanised honeybees a general health issue.

However, the most stunning cases of massive attacks are much less common as we could presume. So, the actual concern falls into risk groups (for example, children, elderly, ill or handicapped people) and to domestic animals, which would have more difficult to scape a attack.

Despite the potential threat they pose, the situation is currently well managed because a large number of comprehensive studies have enabled to perform various steps to control their inhabitants (and even to make the most of them). For several decades, beekeepers have been breeding African American and Africanised bees to make honey and pollinize crops in Centre and South America, becoming one of the most essential honey producers worldwide. To that effect, they apply specific management measures, such as letting only 1 colony to grow inside the hive.

Honey bees alert signs
Installing alert signals minimizes the threat that people come in touch with colonies of bees. Along with the premature detection of people as well as the elimination of potential nesting sites, this activity is a part of the group of preventative measures to avoid the progression of their populations and the interaction of individuals with these organisms.

Even with ‘killer bees’ could be harmful depending on the circumstance, they should not be thought of as a great concern because of the fantastic amount of information there exists about their populations and also about measures to restrain them. However, this case serves as an example of how the impact of humans on ecosystems and the introduction of foreign species may play a dirty trick on native habitats…