The Origins of Honey Bees
Honey bees (Apis mellifera L.) are not native to North America, but they are naturalized and can be found in bee yards and the wild across most of the continent. Honey bees are important components of agriculture in the United States due to their ability to efficiently pollinate a variety of economically important crops and for the production of hive products such as honey and beeswax. The first honey bees brought to America were European races introduced by European settlers in the 1600s, earning them the name “European honey bees,” but the correct common name for them is “western honey bees (WHB).” The home range of the WHB is much larger than just Europe. It spans from western Asia, across Europe, and south through Africa. In contrast, their sister species, the eastern honey bee (Apis cerana F.), ranges from Afghanistan east to Japan and south through Indonesia (Koetz 2013).
Because western honey bees occupy such a vast range, local populations are exposed to many different climates and ecosystems. Northern Europe and western Asia are mostly temperate and forested with very distinct seasons and cold winters. Southern Europe has a very mild climate because of the influence of the Mediterranean and Black Seas. Northern Africa and the middle east are mostly hot and dry deserts with sparse vegetation, while central Africa is dominated by tropical rain forests. Further east and south in Africa, the land is dominated by grassy savannahs with seasons divided more by the amount of rainfall than by temperature. These local climates and ecosystems have influenced the evolution of local honey bee populations and have resulted in the development of approximately two dozen different races (subspecies) of western honey bees, each with specific behaviors and physical characteristics adapted to the conditions of its home range. Even though these races have unique behaviors and characteristics, they are the same species and can breed with each other.
Some honey bee races are known for being gentle and easy to manage, such as the Italian (Apis mellifera ligustica) and Carniolan (A. m. carnica) bees. These races occur where climates are mild, food resources are plentiful much of the year, and pest/predator/parasite pressure is minimal. Due to their mild manner, Italian and Carniolan bees dominate the managed bee population in the United States. Other races of honey bees have adapted to more harsh conditions. For instance, the German (A. m. mellifera) and Russian (A. m. artemisia) honey bees must deal with long, harsh winters. They collect and store large quantities of provisions (honey and pollen) to outlast the winter and are very defensive of their colonies because their survival depends on protecting those resources. The same defensive behavior is common among races that must endure harsh climates and significant predator and pest pressure, which is especially true for many of the races of African honey bees. (Sheppard 2015)
There are at least ten recognized subspecies of honey bees from the African continent. Because most of Africa lies within the tropics, seasons are distinguished more by the amount of rainfall than by temperature. Most of the continent experiences extended dry periods where food resources are extremely limited. Also, predators and hive pests remain active throughout the entire year. For these reasons, many of the races of honey bees from Africa are highly defensive of their colonies and have behavioral adaptations for dealing with predator and parasite pressure.
The races of honey bees from Africa are so distinct in behavior and morphology from their European relatives that they are not easily managed with the traditional Langstroth style equipment. Langstroth hives are the stacked box hives containing removable frames used by the majority of American beekeepers. One subspecies, commonly called the African honey bee (A. m. scutellata), is similar in size and lifestyle to the European races. It mostly lives in eastern and southern Africa’s savannahs, where rainfall is unpredictable, and large predators are a constant threat. It is a defensive race of honey bee that is well adapted to dry tropical savannahs. Colonies of African honey bees have adapted to be smaller and more mobile than European races. They are known to abscond (leave their enclosure) frequently in search of new food resources and to avoid predators and pests. They also swarm more frequently than European races and emphasize brood production over honey storage. When the cavity is filled, the colony will swarm, and African honey bees often select smaller cavities than European honey bees. Because trees are less common in savannahs, African honey bees often nest in rock crevices and animal burrows, and when cavities are not located by swarms, they will build exposed comb on tree branches. While European bees will sometimes extend comb outside of a small cavity, exposed African honey bee comb is often not associated with a cavity at all.
Despite the defensive behavior and propensity to swarm, the African subspecies exhibit some desirable traits such as rapid colony development, pest/parasite resistance, and more efficient pollination. For these reasons, honey bee researchers have explored using African bees in breeding programs with European races to develop productive, pest-resistant bees that are more mild-mannered than the pure African subspecies and better adapted to tropical climates.
Africanized Honey Bees
African honey bees, A. m. scutellata, were brought to tropical Brazil in 1956 by bee experts who hoped to increase honey production in the tropics through a cross-breeding program with the domesticated European races of honey bees already brought to the region. In 1957, 26 swarms headed by African queens were released accidentally and established feral colonies near Sao Paulo, Brazil. These bees hybridized with existing European honey bees, and the hybrid descendants of these honey bees began dispersing across South America. These European-African hybrids are referred to as “Africanized honey bees (AFB).”
While the intent of the breeding program was to develop hybrid bees that possess the most desirable traits of both the European and African races, the reality was that the undesirable traits of African honey bees persisted in feral colonies. The AHB’s defensiveness and swarming behavior made them well-suited for survival in the tropics, and they rapidly spread across South America. As AHBs spread, reports about highly aggressive honey bees that attack people and pets became widely publicized. The movie industry and the media coined the term “killer bee” to describe the AHB and produced sensationalized movies such as “The Swarm,” “The Savage Bees,” and “The Killer Bees” which created inaccurate perceptions of the AHBs.
Although the behavior of AHB is described as “aggressive,” it is more appropriate to describe the behavior as “defensive.” Africanized bees only display this protective behavior when their colonies are disturbed, but they will sting more readily and will defend a larger area around their colonies than European races of western honey bees will. Africanized honey bees do not display defensive behavior when they are foraging or swarming.
The first known AHBs to enter the U.S. from Mexico occurred in the Rio Grande River Valley near Hidalgo, Texas, in October of 1990. Since then, AHBs have spread mostly westward in the U.S. and are now found in Arizona, Arkansas, California, Louisiana, Nevada, New Mexico, Oklahoma, Texas, and Utah. They were also introduced into southern Florida in the early 2000s and have spread northward into the middle part of the state. Isolated AHB colonies have been discovered in other locations in the U.S., but the colonies have been depopulated and were not the result of natural spread. As of 2020, Africanized honey bees are not established in South Carolina (see details below).
USDA Agricultural Research Service 2011
Defensive Behavior of Africanized Honey Bees
Africanized honey bees quickly and vigorously defend their colonies and pursue intruders longer distances than European races will. The venom from an AHB sting has the same potency as European races, and just like other WHB, each AHB worker bee can only sting once; however, encounters with AHBs often result in an increased number of stings because AHBs recruit more workers to the defense response than other races of WHBs. Africanized honey bee attacks often result in as many as ten times as many stings as other WHBs inflict. Most AHB stinging incidences have involved animals such as pets and livestock, and human attacks are rare. Stinging attacks occur when AHB’s perceive a threat to the nest. Typically, the intruder must disturb the nest site to stimulate the defense response. In some cases, the vibrations and exhaust of engines have provoked the bees to sting. This seems terrifying and could be life-threatening, but these events are uncommon even where AHBs are well established.
The best defense for avoiding stings from all stinging insects is to remain aware and avoid disturbing them. If a person encounters a defensive honey bee colony, they should pause briefly to identify where the colony is located to avoid getting closer and further disturbing it. Then the person should calmly and quickly move away from the area. It is important to protect the eyes while creating distance from the nest site. Honey bees instinctively attempt to sting the intruding animal’s head, and stings to the eyes can cause permanent damage. For most people, the pain and swelling caused by honey bee stings are localized and temporary, but a small percentage of people (<5%) develop anaphylaxis when stung by insects. Anaphylaxis is a severe allergic reaction that affects more than just the tissues at the sting location and can result in cardiovascular and respiratory distress. Anaphylaxis is a systemic condition that requires immediate medical attention. The severity of the anaphylaxis might be more intense with AHBs because of the increased number of stings that may occur. Anyone with a history of anaphylaxis should take special care to avoid all insect stings.
Identifying Africanized Honey Bees
Despite its big reputation, the AHB is actually slightly smaller than the EHB, although the differences are so subtle that they cannot be seen with the naked eye. Specialized identification techniques must be used to distinguish the AHBs from the EHBs. It is impossible to simply look at an AHB and distinguish it from an EHB.
Morphometric analysis (measuring landmarks on the bees’ bodies) has been the standard method to differentiate AHB from EHB. Unfortunately, that service, which was once offered by the USDA lab in Arizona, is no longer available. Most states are now using molecular methods for distinguishing subspecies of honey bees, most notable are a PCR (polymerase chain reaction) method developed by Neilson (1999) that looks at patterns of segments of mitochondrial DNA and an SNP (single nucleotide polymorphism) method by Chapman et al. (2015). South Carolina uses the PCR method to determine the percentage of Africanization.
While the identification methods listed above are the only definitive means for determining if bees are Africanized, there are some behaviors that are common among Africanized bees. These behaviors may suggest that a colony is Africanized, and beekeepers should be familiar with them to determine if a colony should be tested.
Dramatic defensive behavior. The defensive response of AHB is much more intense than that of EHB, but there are times when European bees behave defensively and times when Africanized bees are docile. An individual colony’s defensiveness can vary based on weather conditions, time of day, and previous disturbances. Defensiveness can be an indicator, but it is by no means a reliable trait.
- Nest site selection. The home range of AHB is mostly grasslands and is very different from the forested landscapes where EHB live. As a result, AHB are much less selective of their nest sites. They are often observed nesting in the open with an exposed comb and in underground cavities such as under rocks or in animal burrows. Beekeepers in the southwest often find AHB colonies in below-ground utility boxes, irrigation valve boxes, and rock crevices. European bees typically nest in tree cavities, but they will sometimes develop open nests or use utility boxes.
- Colony size and structure. Colonies of AHB are adapted to relocate frequently and build-up rapidly to deal with conditions in the grasslands of Africa, which are prone to drought, fires, floods, predation, and sporadic, short, and intense nectar flows. Most of the comb is dedicated to brood rearing, and a small percentage is dedicated to honey storage. This contrasts with EHBs, which are adapted for developing large stores of food to outlast the long winters in Europe.
- Drone percentage. Africanized bees tend to produce a higher percentage of drones per colony and will build more drone comb than EHB. (Rinderer 1987)
- Propolis. Propolis is the plant resins and sap collected by honey bees to seal gaps and waterproof hives. Some beekeepers report increased propolization in AHB colonies as compared to some EHB colonies.
Africanized Honey Bees and South Carolina
Africanized honey bees are not established in South Carolina. Over the years, reports of defensive colonies have been tested, and the results have never proven that Africanized bees are here. The Clemson Apiary Inspection Program and the Clemson Apiculture and Pollinator Program continue to investigate suspicious colonies.
There are multiple ways AHBs could be introduced into South Carolina. Because the closest feral populations are in central Florida, it is not likely that AHB will migrate into South Carolina without first being detected in Georgia. The most likely ways they will be introduced to South Carolina will be via 1) colonies or queens with Africanized traits that are brought in by a beekeeping operation or 2) by a swarm/colony in a shipping container or cargo coming from an area with AHBs. The Florida populations of AHB came from swarms coming off ships at several deepwater ports. For this reason, South Carolina requires all importations of bees to be permitted through the Apiary Inspection Program, and there are vigorous inspections conducted at ports. Florida conducts inspections of agricultural exports, and all states have some form of apiary inspection and permitting program for monitoring the movement of bees. These systems will reduce the likelihood of introduction and provide early detection if an introduction occurs.
Responding to Suspected Africanized Honey Bees in South Carolina
Beekeepers are the most likely clients to encounter Africanized honey bees if they were to be introduced into South Carolina. If a citizen or beekeeper encounters a honey bee colony that is suspected to be Africanized, the person should immediately contact the office of the State Apiary Inspector (https://www.clemson.edu/public/regulatory/plant-industry/honey-bee/index.html). Inquiries about AHB also can be sent to the Clemson Apiculture and Pollinator Program https://www.clemson.edu/extension/pollinators/apiculture/index.html). An investigator from Clemson’s Regulatory Services will respond to the report and may schedule a visit to the colony location.
Anyone reporting a possible AHB colony needs to be able to 1) confirm that the insects are, in fact, honey bees and not another stinging insect and 2) provide the exact location of the colony. If the colony demonstrates behavioral traits of AHB, then the investigator will collect a sample of bees to have them analyzed. The standard practice for handling a confirmed AHB colony is to depopulate the entire colony. This eliminates the defensive colony and its queen and prevents Africanized traits from being distributed by drones to other colonies in the area.
If AHBs are ever confirmed in South Carolina, the Clemson Apiculture and Pollinator Program will work with the State Apiary Inspector to provide official public notice and will provide response training to beekeepers in the surrounding area. The Atlantic coastal plain is the most likely area of the state to be invaded and allow feral AHB colonies to survive. To date, AHB are not established in South Carolina.
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- Chapman, N.C., B. Harpur, J. Lim, T. Rinderer, M. Allsopp, A. Zayed, B. Oldroyd 2015. A SNP test to identify Africanized honey bee via proportion of ‘African’ ancestry. Molecular Ecology Resources (2015) 15, 1346–1355 doi: 10.1111/1755-0998.12411
- Koetz, Anna, 2013. Ecology, Behaviour and Control of Apis cerana with a Focus on Relevance to the Australian Incursion. Insects Vol. 4 pp. 558-592 10.3390/insects4040558
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- Rinderer, T., A. Collins, L. Helmlich II, R. Danka. 1987. Differential Drone production by Africanized and European honey bee colonies. Apidologie 18 (1) pp. 61-68
- Sheppard, Walter S. 2015. Honey Bee Diversity – Races, Ecotypes, Strains. The Hive and the Honey Bee. Chapter 3 pp. 53-70. Dadant & Sons, Inc. Hamilton, Illinois.