The Arrival of the Killer Bees
My experience began during the period when Americans were first hearing alarming reports about Africanized honey bees, commonly called “killer bees.” These bees did not originate as a naturally occurring new species in South America. In the 1950s, African honey bees were brought to Brazil as part of an effort to develop bees that could produce well in a tropical climate. European honey bees, which had already been introduced into the Americas, were generally better adapted to temperate regions and did not always perform as well under Brazil’s conditions. Some of the African bees escaped into the wild in 1957 and interbred with established European honey bees. Their descendants became known as Africanized honey bees. From Brazil, they spread through much of South America, crossed Central America and Mexico, and were officially detected in the United States in southern Texas on October 19, 1990. They subsequently reached Arizona and New Mexico in 1993 and California in 1994. Their movement from Brazil to the United States therefore took approximately thirty-three years. The term “killer bee” was sensationalized by news reports and popular entertainment, but the underlying danger was real: Africanized colonies could respond to disturbances much faster and in much greater numbers than the European honey bees most American beekeepers were accustomed to handling.
My Ten Hives in the Avocado Orchard
At the time, I had approximately ten honey-bee hives located in or near an avocado orchard in Southern California. This was during the 1990s, when Africanized bees were spreading into the southwestern United States and there was considerable concern among beekeepers and the general public. I had experience being around ordinary honey bees and understood that every hive could behave somewhat differently. Some colonies were calmer than others, and even a normally manageable colony could become defensive because of weather, a lack of nectar, disturbance, queen problems or other conditions. What happened with two of my colonies, however, was unlike the normal variation I had previously seen. I did not have the bees tested, and therefore I cannot prove that either colony had become Africanized. My conclusion was based entirely upon the timing, the unusual behavior and the sudden level of aggression. I can only describe exactly what I witnessed and explain why, at the time, I believed that something had changed within those colonies.
The Day the Colony Appeared to Walk Away
The first strange incident occurred while I was working in the avocado orchard. I noticed activity around one hive that I could not explain then and still cannot explain with certainty today. It appeared that an enormous portion of the colony was leaving the hive together. Instead of taking flight in the way I would expect from a swarm, large numbers of bees seemed to be moving along the ground. The bees appeared almost as though the entire colony was walking away from the hive. I watched them move outward and then, for reasons I did not understand, turn around and go back inside. It was an extraordinary sight. Honey bees sometimes gather outside a hive in large numbers because of heat or crowding, a behavior commonly called bearding, and colonies can also abscond from a hive under stressful conditions. What I saw did not look to me like ordinary bearding, and the colony did not complete an apparent departure. It looked as if the bees had started to leave and then reversed themselves. I did not disturb the hive at that moment, but I remember thinking that something very unusual had just happened.
The Attack from One Hundred Feet Away
A day or two later, I returned to the orchard and was approximately one hundred feet from that same hive. I was not opening it, striking it or knowingly interfering with it. Without warning, approximately ten bees attacked me very aggressively, concentrating around my hair and face. This was not the behavior I expected at that distance from one of my managed colonies. European honey-bee colonies certainly can defend themselves, and a few guard bees may confront a person close to the entrance, especially if the colony has recently been disturbed. This attack felt different because of the distance, the suddenness and the concentration around my head. I immediately thought that something about this hive had changed. Africanized honey bees do not possess more potent venom than ordinary honey bees, but they can be more dangerous because a defensive response may involve many more bees and may extend farther from the colony. The bees that attacked me were not scientifically identified, so I cannot say that they were Africanized. Nevertheless, this was occurring during the period when Africanized bees were entering California, and I had never experienced comparable behavior from my hives before.
My Decision to Destroy the Colony
Because the hives were near my house and near areas where people could be present, I believed that I could not safely ignore what had happened. That evening, after the temperature had cooled and the foraging bees had returned, I decided that the colony had to be destroyed. I used a soap-and-water solution, which kills bees by breaking the surface tension and coating their bodies. This was not a decision I made casually. A beekeeper normally wants to preserve a colony, particularly one that has required time and work to establish. However, a dangerously defensive hive located near a residence can become a serious liability. My concern was not simply that I had been stung. It was that someone unfamiliar with the hive—a visitor, neighbor, worker or child—might unknowingly approach it and trigger a much larger defensive response. At that time, news reports were describing severe attacks involving Africanized colonies, including attacks in which people and animals received large numbers of stings. Whether or not my colony was Africanized, I had direct evidence that it had become aggressive at a considerable distance. I therefore destroyed it rather than risk waiting for a more serious incident.
Testing the Remaining Hives
After the first colony was gone, I continued to think about what had happened. Several months later, I decided that I needed a simple way to observe whether any of the remaining hives reacted abnormally to disturbance. Occasionally, toward evening when the temperature was cooler and most of the bees had returned, I would tap on the outside of a hive and watch the entrance. This was not a scientific test for Africanization, and it should not be represented as one. Colony temperament can be affected by many conditions, and deliberately disturbing a potentially defensive hive can be dangerous. At the time, however, I was trying to determine whether any of my other colonies showed a reaction comparable to the first one. A normal response might involve several guard bees coming out to investigate. The reaction from one particular colony was different. A substantial number of bees emerged, moved onto the landing board and remained there facing me. They did not immediately attack. They simply came out together and appeared to watch me. It was the coordinated scale of the response that caught my attention. The behavior was quiet, but it did not feel normal.
The Second Colony Becomes More Aggressive
I observed the second colony again on later occasions. Each time, its response appeared to become stronger and more aggressive. I was aware that a colony’s temperament could change if it became queenless, if a defensive queen had taken over, if it was being robbed, if animals had disturbed it or if environmental conditions were placing it under stress. I was also aware that Africanized colonies could replace or genetically alter managed European colonies when Africanized drones mated with new queens, or when an Africanized swarm occupied an abandoned hive. Without genetic, morphometric or laboratory testing, outward appearance and defensiveness alone could not establish the ancestry of the bees. Nevertheless, the practical question for me was not simply what label should be attached to the colony. The practical question was whether it was safe to maintain near my home. As the defensive response increased, I concluded that it was not. I eventually euthanized the second colony as well. Once again, I chose to remove a potentially dangerous hive rather than wait until someone received dozens or hundreds of stings.
Why I Suspected Africanization
I never received laboratory confirmation that either hive contained Africanized bees, and I do not want to turn a personal conclusion into a proven scientific fact. There were other possible explanations for the behavior. A colony can become unusually defensive because of its genetics without being fully Africanized. It may also respond aggressively because of queen changes, predators, repeated disturbance, food shortage or disease. Even experienced beekeepers cannot reliably identify Africanized bees merely by looking at them because they closely resemble European honey bees. Formal identification has historically required measurements, genetic methods or a combination of tests. Even so, the timing was difficult for me to dismiss. Africanized bees entered California during the 1990s, precisely when these incidents occurred. The long-distance attack, the unusually large defensive response and the increasing aggression of the second colony were consistent with the characteristics being reported at the time. My belief remains that Africanization was the most likely explanation, but it remains an interpretation of what I observed rather than a verified identification.
Swarming, Absconding and Rapid Colony Reproduction
One reason Africanized bees spread so successfully was their tendency to reproduce, swarm and relocate more frequently than many managed European colonies. Swarming occurs when part of a colony leaves with a queen to establish another colony. Absconding is different because virtually the entire colony abandons its nest, often because of disturbance, food shortages, parasites or unsuitable environmental conditions. Africanized bees are generally more inclined to abscond and occupy small or temporary cavities. This allows them to establish colonies in places where people may not expect to find honey bees, including containers, utility structures, abandoned equipment and spaces around buildings. Their reproductive behavior helped them move across tropical and subtropical regions far more rapidly than they could have spread through the movement of a few individual bees. Whether the mass of bees I observed walking outside the first hive was preparing to swarm, abscond or simply reacting to some temporary condition remains unknown. The colony returned inside, and I did not inspect it closely enough at that moment to establish what was taking place. I can only say that the event preceded the unexpected attack and was the first indication that the colony was behaving differently.
Did Varroa Mites Eliminate Africanized Bees?
At the time, I believed that Varroa mites might eventually take care of Africanized bees living in unmanaged colonies. Varroa destructor is a serious parasite of honey bees. The mites reproduce in capped brood cells, feed on developing and adult bees, and spread damaging viruses. They have contributed to the death of enormous numbers of managed and unmanaged European-derived honey-bee colonies. It therefore seemed reasonable to assume that wild Africanized colonies would eventually suffer the same fate. Scientific evidence, however, does not support the conclusion that Varroa mites eliminated Africanized honey bees. Varroa mites can and do infest Africanized colonies, but many Africanized populations demonstrate greater natural tolerance or resistance than susceptible European-derived colonies. Studies of untreated Africanized bees in Latin America have found relatively low mite-infestation levels, while research has identified traits such as grooming, shortened brood-development time, reduced mite reproduction and colony-level survival. This does not mean that Africanized bees are immune to Varroa or that no colonies die from mites and mite-transmitted viruses. It means that the relationship is more complicated than I originally believed. In many regions, Africanized bees have persisted in the presence of Varroa rather than being removed by it.
What May Have Happened Around My Property
Looking back, it is possible that a feral swarm with Africanized ancestry entered one of my hive boxes, that a replacement queen mated with Africanized drones, or that the colonies simply developed defensive genetics unrelated to the main Africanized expansion. It is also possible that stress within the hives amplified an already defensive temperament. I had no genetic testing and no official inspection, so none of these explanations can now be demonstrated. I also cannot prove that the Varroa mite later reduced Africanized colonies around my property. Africanized bees continued to establish themselves in parts of California and the broader Southwest, although their distribution and behavior varied with climate, managed-bee genetics and local conditions. The absence of another obvious incident near my hives would not prove that they had disappeared. Colonies can move, die, be replaced or become less noticeable. My original belief that Varroa would destroy the wild population was understandable, considering the devastation the mite caused in ordinary managed colonies, but current evidence indicates that Africanized populations are often better able to coexist with the parasite.
What the Experience Taught Me
The experience taught me to pay attention when a familiar animal begins behaving in an unfamiliar way. I knew how my colonies normally reacted when I approached them, and the behavior of these two hives did not fit that pattern. At the same time, the experience also taught me the limits of personal observation. I can accurately report the bees walking on the ground, the sudden attack from approximately one hundred feet away, the unusual gathering on the landing board and the increasing aggression that followed. I cannot accurately claim that laboratory testing proved the colonies were Africanized, because no such testing was performed. My conclusion was based upon circumstances and behavior. I believed then, and still believe, that Africanization was a reasonable explanation, but I recognize that other biological and environmental explanations were possible. Because the colonies were situated close to my home, I made the decision that appeared safest under the circumstances. I destroyed two colonies that had become unpredictable rather than risk a severe attack on someone who had no warning that the bees might react aggressively.
Conclusion
The arrival of Africanized honey bees in the United States was not a sudden invasion but the end of a decades-long expansion that began after African bees escaped in Brazil in 1957. By the time they officially reached Texas in 1990 and California in 1994, the public had already heard years of frightening predictions about “killer bees.” Some of those reports were exaggerated, but Africanized colonies could present a genuine hazard because of the speed, distance and size of their defensive response. My own encounters occurred during that period and involved behavior that was dramatically different from what I had previously observed among my ten hives. I cannot prove that the bees were Africanized, but their behavior convinced me that the colonies were unsafe to maintain near a residence. I once assumed that Varroa mites would eventually eliminate Africanized colonies from the wild. Research now shows that this was unlikely. Although Varroa mites infest them, Africanized honey bees often possess stronger natural defenses against the parasite and have survived alongside it in many regions. My experience therefore remains what it has always been: a beekeeper’s direct observation of two dangerously defensive colonies during the arrival of Africanized bees in California, followed by a decision made to protect the people living and working nearby.
Addendum: Why I Chose Not to Wait
Another factor influenced my decision that is worth mentioning. From my years of keeping bees, I understood that a colony often becomes increasingly defensive as it settles into a location. Once a queen is well established, brood production increases, food reserves accumulate, and the workers have more investment in defending their home. As the colony grows, there are simply more guard bees available to respond to perceived threats. While defensiveness can vary for many reasons—including genetics, season, nectar availability and disturbance—it is generally recognized that colonies with more brood and resources often defend them more vigorously than newly established swarms. I knew this at the time, and it influenced my decision. My concern was that if these unusually aggressive colonies continued to establish themselves and expand, their defensive behavior might escalate further. Because the hives were located near my home and areas where other people could be present, I did not believe it was prudent to wait and see whether the problem became worse. Whether the colonies were Africanized or simply unusually defensive, I felt that removing them immediately was the safest and most responsible course of action.
Related Beekeeping Guides
Beekeeping the Right Way for Pollination and Colony Stability (Pillar)
Large Beekeeping Systems Pillar: Stability and Performance Optimization of Colonies
Advanced Beekeeping: Productivity and Colony Health
Insects and Pollinators — USDA Natural Resources Conservation Service
Addendum: A Possible Explanation—Washboarding Behavior
Years after this unusual event, I learned about a little-understood honey bee behavior known as washboarding. During washboarding, large numbers of worker bees line up on the front of the hive and repeatedly move back and forth in synchronized motions across the wood surface. Researchers have observed this behavior for decades, but no single explanation has been confirmed. Proposed theories include cleaning the hive entrance, applying or redistributing wax or propolis, smoothing surfaces, or responding to chemical cues within the colony. In my case, I did not recognize the behavior at the time because the bees appeared to be moving together across the ground before turning and returning to the hive. Whether what I witnessed was an unusual variation of washboarding, a related colony behavior, or something entirely different remains unknown. I cannot say that it was washboarding, only that learning about this phenomenon later provided one possible explanation for an event that has puzzled me ever since.