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Are Killer Bees Moving North? Michigan, Indiana, Ohio, and the Midwest

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Every few years a headline warns that “killer bees” are marching north. Midwesterners, including beekeepers in Michigan, Indiana, and Ohio, reasonably want to know whether Africanized honey bees are on the way. The short answer: as of this writing, we found no extension or state agriculture report of an established Africanized honey bee population in Michigan, Indiana, or Ohio. The bees’ northern edge has moved very little in decades, and scientists think climate is the main reason.

Here’s where the edge sits now, why the spread slowed, what could change it, and what Midwestern beekeepers can do. For the full state list, see Where Do Killer Bees Live?. This post is part of our Killer Bees 101 guide.

Where Africanized bees are established today

In a June 2025 statement, Mississippi State University Extension listed the states where Africanized honey bees are established: Texas, New Mexico, Arizona, southern California, southern Nevada, Oklahoma, Louisiana, southern Arkansas, and large areas of southern Florida. A University of Florida (UF/IFAS) profile, using data through 2012, also lists Alabama. USDA has also reported them in Puerto Rico and the U.S. Virgin Islands.

Not one Midwestern or Great Lakes state is on those lists.

A fast spread that hit the brakes

The arrival was dramatic. USDA ARS records the first U.S. detection on October 15, 1990, when a swarm turned up in a research trap near Hidalgo, Texas. UF/IFAS describes the earlier spread through South and Central America as moving 200 to 300 miles per year, “one of the most successful biologically invasive species of all time.” (The backstory is in The History of Killer Bees.)

Then it slowed. As early as 1996, USDA ARS wrote that the spread had been “much slower than predicted,” pointing to interbreeding with resident European bees, disease, parasites, and cold weather. UF/IFAS notes that in the Northern Hemisphere the bees are currently found only below about 34° latitude, and that they never established south of about 32° in the Southern Hemisphere. For reference, Ohio, Indiana, and Michigan sit roughly between 38° and 48° north.

California offers a more precise picture. A 2015 study in PLOS ONE by UC San Diego researchers sampled foraging honey bees from the Mexican border to southern Oregon. About 65 percent of workers in San Diego County carried African maternal DNA. North of 35.5° N, though, only 6 of 233 bees did, and the northernmost detection was about 40 km south of Sacramento. The authors concluded that range expansion had slowed considerably from the bees’ maximum rates.

Why the bees struggle in the North

Cold winters

UF/IFAS says plainly that African-derived bees “do not survive in temperate climates as well as European bees do.” Part of the reason is how they handle food. Africanized colonies evolved where something is usually in bloom, so they store proportionately less honey than European colonies and invest instead in fast growth and frequent swarming. A colony that doesn’t stockpile honey has a hard time getting through a long northern winter.

The PLOS ONE authors reviewed two older predictions of the northern limit: one placing it where the coldest month averages below about 16°C (61°F), and another based on 120 consecutive winter days not exceeding 10°C (50°F). Africanized bees have already overwintered north of the first prediction in California, and haven’t come close to the second, which would have put them along the West Coast to Canada. In other words, temperature matters, but no simple line predicts exactly where they stop.

Wet climates

Rainfall may matter too. In 2004 USDA ARS reported that one of its entomologists had found a strong correlation between more than 55 inches of rain, spread evenly through the year, and an almost complete barrier to Africanized bee spread. ARS stressed that it was a correlation, not a proven cause.

Strong European bee populations

USDA ARS has long argued that “a healthy population of European bees, kept that way by beekeepers regularly requeening hives with honey bees of known docile parentage, may be an area’s best defense against the spread of Africanized hybrids.” The Midwest has plenty of managed European colonies.

Could they show up anyway?

Yes, as isolated arrivals. Honey bees can hitch rides on ships, trucks, and cargo, and those events have happened well outside the main range:

  • Florida: UF/IFAS says the state’s first documented Africanized bees appeared in 2001 near the Port of Tampa, and by 2003 they had established colonies there.
  • Mississippi: Extension specialist Jeff Harris says the state’s only confirmed identification in 13 years was a colony in Pass Christian that likely arrived by ship. State officials destroyed it and monitored swarm traps for at least a year without finding more. They treated it as an isolated event, not a migrating front.
  • Georgia, 1980: The PLOS ONE paper notes a feral colony collected in Georgia in 1980, a decade before the bees reached Texas, carried African mitochondrial DNA, suggesting an earlier port introduction.

The lesson for the Midwest is that a stray swarm arriving by freight isn’t the same as an established population. One colony needs to survive several winters and keep reproducing before scientists would call the bees established, and the climate works against that.

What about climate change?

Researchers expect warming to shift suitable range north over time. The PLOS ONE authors noted that a warming climate could move the predicted range limit and that the northern edge “may covary to some degree with fluctuations in winter temperatures.” NC State Extension, reviewing its guidance in 2024, still calls Africanized bees’ arrival in North Carolina “fairly likely” in the coming years. That’s a reason to monitor, not a reason to panic. Nothing we found predicts Africanized bees establishing in the Great Lakes states any time soon.

Most northern “killer bee” reports are European bees

Ohio State University entomologists described a 2024 case in which a southwest Ohio beekeeper became convinced one of his colonies was Africanized, killed it, and sent in samples. OSU measured the wings: ordinary western honey bees. UF/IFAS, Mississippi State, and USDA all note that some European colonies are very defensive. A hot colony up north is far more likely to be queenless, harassed, or carrying cranky European genetics than to be Africanized. Read the Ohio details in Are There Killer Bees in Ohio?

What Midwestern beekeepers can do

  1. Test before you destroy. If you truly suspect Africanization, contact your state apiary inspector. Michigan State University Extension’s 2025 guide notes that confirmation requires molecular testing and lists labs, including the Purdue University Honey Bee Lab, that test for Africanized genetics. It also reminds beekeepers to check whether their state requires reporting.
  2. Requeen defensive colonies with queens of known gentle stock.
  3. Mark every queen, as NC State Extension recommends, so you’ll notice if one is replaced, for example by a foreign swarm.
  4. Know where your bees and queens come from. Mississippi State notes that beekeepers in its state avoid buying stock that may have mated with Africanized drones.
  5. Learn the identification basics. See How to Identify Africanized Bees.

Frequently asked questions

Are there killer bees in Michigan?

We found no Michigan State University Extension or state report of an established Africanized population in Michigan. MSU’s guidance notes that any suspected case requires molecular testing to confirm.

Are there killer bees in Indiana?

We found no report of an established Africanized population in Indiana. Purdue University’s Honey Bee Lab is listed as one of the labs that test bees for Africanized genetics.

How far north have killer bees spread?

UF/IFAS says they’re currently found only below about 34° north latitude. In California, the 2015 PLOS ONE study detected African DNA as far north as about 40 km south of Sacramento, but found Africanized bees to be a clear minority north of about 35.5°.

Will global warming bring killer bees to the Midwest?

Warming could shift their potential range northward over time, and scientists continue to monitor the edge. Current research and extension guidance don’t predict establishment in the Great Lakes states in the near term.

Can a killer bee swarm arrive on a truck or ship?

Yes. Florida’s first Africanized bees were found near the Port of Tampa, and Mississippi’s single confirmed colony likely arrived by ship. An isolated arrival is different from an established population.

Related reading

Sources

  • Mississippi State University Extension, “Africanized honey bees not established in Mississippi” (2025): https://extension.msstate.edu/news/feature-story/2025/africanized-honey-bees-not-established-mississippi
  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee”: https://edis.ifas.ufl.edu/publication/IN790
  • UF/IFAS EDIS ENY-170, “Living with the African Honey Bee”: https://ask.ifas.ufl.edu/publication/IN1205/pdf
  • USDA ARS, “Africanized Honey Bees: The March North Has Slowed,” Agricultural Research (1996): https://agresearchmag.ars.usda.gov/1996/mar/forum/
  • USDA ARS, “The Latest Research on Africanized Honey Bees” (2004): https://www.ars.usda.gov/news-events/news/research-news/2004/the-latest-research-on-africanized-honey-bees/
  • Kono & Kohn, “Range and Frequency of Africanized Honey Bees in California (USA),” PLOS ONE (2015): https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137407
  • Ohio State University BYGL, “Myths and facts – Africanized honey bees” (2024): https://bygl.osu.edu/node/2431
  • Michigan State University Extension, “Diagnostic labs and services for beekeepers” (2025): https://www.canr.msu.edu/news/diagnostic-labs-and-services-for-beekeepers
  • NC State Extension, “Africanized Honey Bees: Prevention and Control”: https://content.ces.ncsu.edu/africanized-honey-bees-prevention-and-control

Killer Bees vs. Murder Hornets, Yellowjackets, and Wasps: How They Compare

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“Killer bees” and “murder hornets” are two of the scariest-sounding insect names in American news. They’re often mentioned in the same breath, but they’re completely different animals with different risks. And for most people in the northern half of the country, the stinging insect that actually causes trouble every summer is neither one. It’s the yellowjacket.

This guide compares Africanized honey bees, the northern giant hornet, yellowjackets, and other common wasps, and shows you how to tell a bee from a wasp at a glance. It’s part of our Killer Bees 101 guide.

The short version

“Killer bee” (Africanized honey bee) “Murder hornet” (northern giant hornet) Yellowjacket
What it is A honey bee, Apis mellifera The world’s largest hornet species, Vespa mandarinia A predatory social wasp, Vespula spp.
U.S. status Established across the southern U.S. Declared eradicated from the U.S. in December 2024 Common nationwide; the German yellowjacket is Ohio’s dominant species
Stings Once, then the bee dies WSDA says its sting is more dangerous than a honey bee’s Can sting repeatedly
Main danger to people Mass stinging when a nest is disturbed Dangerous sting, but no known U.S. population since eradication Painful stings near nests and food; allergy risk
Main danger to bees Can take over European honey bee colonies Can destroy a honey bee colony within hours Not a major threat to healthy colonies in extension guidance cited here
Body Fuzzy, golden-brown Very large hornet Smooth, shiny, bright yellow and black

Killer bees: honey bees with a hair trigger

Africanized honey bees are the same species as ordinary honey bees. UF/IFAS entomologists stress that their venom is no more potent than a European honey bee’s; the difference is behavior. A disturbed European colony might send out 10 to 20 guard bees. A disturbed Africanized colony may send out several hundred and stay agitated for days.

Like all worker honey bees, an Africanized bee has a barbed stinger. It stays in the skin, and the bee dies soon after stinging. The danger comes from numbers. That’s covered in depth in How Dangerous Is a Killer Bee Sting?

Africanized bees are established in Texas, New Mexico, Arizona, southern California, southern Nevada, Oklahoma, Louisiana, southern Arkansas, and large parts of southern Florida, according to Mississippi State University Extension. They are not established in Ohio or the Midwest. See Where Do Killer Bees Live?

“Murder hornets”: the northern giant hornet

The insect nicknamed the “murder hornet” is the northern giant hornet, Vespa mandarinia, which USDA’s Animal and Plant Health Inspection Service (APHIS) calls the world’s largest hornet species. Its biggest threat was to honey bees: APHIS says it is “known for its ability to decimate a honey bee colony within hours,” and WSDA says the hornets can kill an entire hive in as little as 90 minutes. WSDA also notes that their sting is more dangerous to people than a honey bee’s.

Its U.S. story is short:

  • August 2019: first detected in North America, in British Columbia, Canada.
  • December 2019: confirmed in Washington State near Blaine.
  • 2020–2021: the Washington State Department of Agriculture (WSDA) and partners found and destroyed four nests, all in alder tree cavities. Teams used radio tags to track live hornets back to their nests.
  • December 18, 2024: after three years with no confirmed detections, WSDA and USDA declared the northern giant hornet eradicated from Washington and the United States.

APHIS notes that nearly half of the confirmed detections came from public reports. WSDA has said the hornets “got here once and they could do it again,” so agencies still ask the public to report suspicious large hornets. But as of the eradication announcement, there is no known population in the U.S.

Killer bees vs. murder hornets: which is more dangerous?

In today’s United States, Africanized honey bees are the bigger practical concern because they’re actually established here. They are a serious hazard where they live, especially to people who disturb a nest without knowing it, and to pets and livestock that can’t escape. The northern giant hornet had a more dangerous individual sting and was a severe threat to honey bee colonies, but it has been eradicated.

Yellowjackets: the real late-summer problem up north

Ohio State University’s Ohioline fact sheet on yellowjackets explains why these wasps dominate stinging complaints in the North:

  • The German yellowjacket first appeared in Ohio in 1975 and is now the dominant species in the state.
  • Colonies are annual. Queens overwinter, start nests in spring, and by August and late September nests reach about 4,000 to 5,000 workers.
  • Nests are usually in old rodent burrows, mulch, rotted stumps, wall voids, and ceilings.
  • From August to October, their diet shifts from protein to sweets, which is when they show up at picnics, trash cans, and soda cans.
  • Unlike honey bees, yellowjackets can sting repeatedly, and they often do near the nest.

NC State Extension adds a point many people don’t expect: wasps such as yellowjackets and European or bald-faced hornets are often mistaken for honey bees, and “many of these wasps can be even more defensive than Africanized honey bees.”

Hornets and paper wasps

  • Bald-faced and yellow hornets build the familiar papery, football-shaped nests hanging in trees and shrubs or under eaves. OSU notes their life cycle and habits are similar to yellowjackets’.
  • Paper wasps build open, umbrella-shaped combs under eaves and railings. University of Arizona Extension describes wasps as more slender than bees, with smooth, shiny bodies and narrow hind legs. All of them can sting many times.

Bee or wasp? How to tell at a glance

From Ohio State and University of Arizona Extension:

  • Hair: Honey bees are fuzzy and robust. Yellowjackets and other wasps are smooth, shiny, and mostly hairless.
  • Legs: Honey bees have flattened, hairy hind legs and often carry yellow or orange pollen loads. Wasp hind legs are thin and cylindrical.
  • Waist: Wasps have a noticeably thin waist.
  • Wings: OSU notes wasps and hornets fold their wings lengthwise at rest and fly with their legs close to the body.
  • Color: Yellowjackets are bright, sharp yellow and black. Honey bees are golden-brown and banded, not glossy.
  • Nests: Honey bees build wax comb, usually inside a cavity. Wasps build paper nests, either enclosed (yellowjackets, hornets) or open (paper wasps).
  • Behavior around food: If it’s crawling into your soda can in September, it’s almost certainly a yellowjacket.

What to do about each one

Africanized honey bees (southern U.S.): Don’t approach or disturb the colony. Keep at least 100 feet away, as USDA ARS recommends, and call a beekeeper or trained pest control operator. If attacked, run to a car or building and cover your face. Our step-by-step guide is What to Do If Killer Bees Attack.

Northern giant hornets: If you’re in the Pacific Northwest and see what you think is a giant hornet, photograph it from a safe distance and report it to your state department of agriculture. Don’t try to handle it.

Yellowjackets and hornets: OSU advises:
– Don’t mow over or disturb a ground nest, and watch where you step in mulch and tall grass.
– Never plug the entrance of a nest in a wall void, because disturbed wasps can find their way into the house.
– Never shine a flashlight at a nest entrance at night; the insects fly toward the light.
– Keep drinks covered and trash cans closed in late summer.
– OSU “highly recommend[s]” hiring a professional to kill and remove wasp nests.

For any stinging insect: OSU says to seek medical attention after more than ten stings, or stings in the mouth or around the eyes, and to get emergency care right away for trouble breathing or swallowing, throat tightness, confusion, or fainting.

Frequently asked questions

Are murder hornets still in the United States?

No known population remains. WSDA and USDA declared the northern giant hornet eradicated from Washington and the U.S. on December 18, 2024, after three years without confirmed detections.

Do murder hornets kill killer bees?

Northern giant hornets prey on honey bee colonies, and APHIS says they can destroy a colony within hours. Their U.S. range (northwest Washington) and the Africanized bees’ range (the southern U.S.) never overlapped, though.

Which stings more, a yellowjacket or a killer bee?

An individual yellowjacket can sting repeatedly, while a honey bee stings once and dies. Africanized bees are dangerous because hundreds may sting at once when a nest is disturbed.

Are killer bees a type of wasp?

No. They’re honey bees, the same species that beekeepers keep for honey. Wasps belong to a different family.

What insect stings the most people in Ohio?

In late summer, yellowjackets, especially the German yellowjacket, which OSU calls the dominant species in Ohio. See Are There Killer Bees in Ohio?

Related reading

Sources

  • USDA APHIS, “APHIS in Action: Victory Over the World’s Largest Hornet Species”: https://www.aphis.usda.gov/news/agency-announcements/aphis-action-victory-over-worlds-largest-hornet-species
  • Washington State Department of Agriculture, news release on northern giant hornet eradication (Dec. 18, 2024): https://agr.wa.gov/about-wsda/news-and-media-relations/news-releases?article=41658
  • Ohio State University Ohioline HYG-2075, “Yellowjackets”: https://ohioline.osu.edu/factsheet/HYG-2075-11
  • NC State Extension, “Africanized Honey Bees: Prevention and Control”: https://content.ces.ncsu.edu/africanized-honey-bees-prevention-and-control
  • UF/IFAS EDIS ENY-147, “Differences Between European and African Honey Bees”: https://ask.ifas.ufl.edu/publication/IN784
  • Mississippi State University Extension, “Africanized honey bees not established in Mississippi” (2025): https://extension.msstate.edu/news/feature-story/2025/africanized-honey-bees-not-established-mississippi
  • University of Arizona Extension, “They are called Africanized Honey Bees”: https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/195020a.pdf
  • USDA ARS Carl Hayden Bee Research Center, “Africanized Honey Bees Overview”: https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/docs/africanized-honey-bees/africanized-honey-bees-overview/

How to Identify Africanized Bees (and an Africanized Hive)

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People want a simple field mark for Africanized “killer” bees: a color, a stripe, a size. There isn’t one. Mississippi State University Extension bee specialist Jeff Harris put it bluntly in 2025: European honey bees and Africanized bees “look exactly alike, and even experienced beekeepers can’t tell them apart just by looking.”

So how do scientists identify them? With measurements and DNA. And how should a homeowner or beekeeper decide whether a colony deserves extra caution? By watching how it behaves. This guide covers both. It builds on What Are Killer Bees? and is part of our Killer Bees 101 guide.

Why you can’t identify Africanized bees by eye

Africanized and European honey bees are the same species, Apis mellifera. UF/IFAS entomologists say Africanized workers are only about 10 percent smaller, a difference so subtle that it’s “nearly impossible to differentiate between the two without specific measurements and/or laboratory testing.”

Color doesn’t help either. Both European and Africanized colonies range from golden to dark, depending on their mixed ancestry. University of Arizona Extension captions its side-by-side photo of the two bees with a warning that, despite the color difference in that particular image, they normally can’t be identified by eye.

That’s why the safe rule in the southern U.S. is the one Arizona extension agents give: in areas where Africanized bees are established, treat any wild honey bee colony as potentially Africanized.

How labs identify Africanized bees

1. Morphometrics: measuring the bee

Morphometric analysis measures body parts and wing features and compares them to reference populations. UF/IFAS notes it has been used to separate honey bee races since the 1960s and remains the first round of identification when a suspect colony turns up.

The best-known screening method is FABIS (Fast Africanized Bee Identification System), developed by USDA scientists H. A. Sylvester and Thomas E. Rinderer in 1987. It starts with the length of the forewing. The FABIS critical value for forewing length is 9.001 mm. Samples averaging below that point toward Africanization and are sent on for more testing.

Ohio State University entomologists showed how this works in 2024. A Hamilton County beekeeper sent in bees from a hot-tempered colony he believed were “killer bees.” OSU measured the forewings of 10 workers. They averaged 9.27 mm, above the cutoff. The bees were ordinary western honey bees, just a defensive colony. (The beekeeper had already destroyed the colony, which is why OSU urges testing first.) OSU notes that any beekeeper with a good microscope, forceps, glass slides, and a millimeter ruler can run this first screen.

If FABIS results are inconclusive, Florida’s agriculture department uses a more detailed morphometric test called USDA-ID, according to UF/IFAS.

2. Genetics: reading the DNA

Morphology can be fooled by hybrids, so the strongest confirmation is genetic. UF/IFAS says genetic analysis is often needed when suspect bees are hybrids. Michigan State University Extension’s 2025 guide to diagnostic labs states that confirmation of Africanized honey bee genetics “is required through standardized testing using molecular analysis.”

One common approach looks at mitochondrial DNA, which passes from queen to daughters. Researchers at UC San Diego, writing in PLOS ONE in 2015, used a simple restriction test on the mitochondrial cytochrome b gene to tell bees with African maternal ancestry from those with European ancestry, and found a single DNA “barcode” marker that does the same job.

Where samples go

Testing options change, so check before you ship anything:

  • The USDA ARS Carl Hayden Bee Research Center in Tucson says it can no longer analyze honey bee identification samples (morphometrics); that service has been discontinued.
  • Michigan State’s diagnostic-lab table (adapted from the Apiary Inspectors of America) lists labs that test for Africanized genetics, including the Purdue University Honey Bee Lab and North Carolina State University.
  • In many states, the state apiary inspector collects samples. MSU advises checking your state’s rules, since some states require you to report suspected Africanized colonies.

Signs of an Africanized hive

Behavior is what sets Africanized colonies apart. None of these signs is proof, and European colonies can show some of them too. But a colony that checks several boxes deserves distance and a professional.

Defensive response

UF/IFAS summarizes the difference:

European colony Africanized colony
Guard bees that respond 10 to 20 Several hundred
Distance of disturbance that triggers a response Up to about 20 feet Up to about 120 feet
Time to calm down 1 to 2 hours May stay defensive for days
Stings from a disturbed colony 10 to 20 100 to 1,000

Source: UF/IFAS EDIS ENY-147.

UF/IFAS’s “Living with the African Honey Bee” adds that Africanized bees may pursue an intruder 400 yards or more.

Head-butting

A USDA Forest Service safety guide notes that Africanized guard bees patrol territories extending 30 meters or more from the nest and drive intruders away by head-butting: flying straight at the target with a high-pitched buzz. If bees start bumping your face or hat, the guide says to retreat quickly.

Unusual nest sites

According to UF/IFAS, European bees prefer dry, protected cavities of around 10 gallons, such as hollow trees. Africanized colonies will use cavities of 1 to 5 gallons, including:

  • Water meter and utility boxes
  • Cement blocks, old tires, and junk piles
  • Cavities in the ground, even damp ones
  • Exposed spots, such as combs hanging from a tree branch

Swarming, absconding, and other colony traits

UF/IFAS lists several more differences: Africanized colonies swarm and abscond far more often, are more “flighty” (more bees leave the comb when the hive is opened), use more propolis, raise proportionally more drones, and store proportionately less honey. Read more in Killer Bee Swarm Season.

The big caveat

A 1996 USDA ARS forum on the bees’ spread made the point that the defensive behavior of the two types “can completely overlap; that is, some aggressive European bees are more prone to stinging attacks than some milder Africanized bees.” That’s exactly what OSU found in Ohio. A mean colony is not proof of Africanization, especially outside the known range.

What to do if you suspect Africanized bees

If you’re a homeowner:

  1. Keep away from the nest and keep children and pets inside. USDA ARS recommends at least 100 feet of distance from any Africanized colony.
  2. Don’t try to kill or remove the bees yourself. University of Arizona Extension warns against spraying, burning, or otherwise disturbing colonies.
  3. Call a trained beekeeper or pest control operator. In Florida, state guidance is to use a registered beekeeper or trained pest control operator.
  4. If anyone is being stung, run for shelter and call 911. See What to Do If Killer Bees Attack.

If you’re a beekeeper:

  1. Test before you destroy. OSU’s Ohio case shows why.
  2. Contact your state apiary inspector. NC State Extension recommends calling the inspector so a sample can be taken.
  3. Requeen defensive colonies with a queen of known gentle stock, as NC State Extension and UF/IFAS recommend.
  4. Mark your queens. NC State Extension advises marking every queen so you’ll notice if one is replaced, for example by an Africanized swarm taking over the colony.

Frequently asked questions

Can you tell an Africanized bee by its color?

No. Color varies in both European and Africanized bees. Mississippi State and UF/IFAS specialists agree that the two can’t be told apart by looking.

What is the FABIS test?

The Fast Africanized Bee Identification System is a USDA-developed morphometric screen. It starts with forewing length; a sample averaging under the 9.001 mm critical value is flagged as possibly Africanized and needs further testing.

Can I test my own bees for Africanization?

You can run the first FABIS wing-length screen with a microscope and ruler, as OSU describes. Confirmation requires lab analysis, usually DNA testing through a diagnostic lab or your state apiary program.

Does an aggressive colony mean I have killer bees?

Not necessarily. European colonies can be very defensive because of genetics, a missing queen, hunger, or pests. In 2024 OSU tested a suspected “killer bee” colony from Ohio and found ordinary western honey bees.

Does the USDA still identify Africanized bees?

The USDA ARS bee lab in Tucson says it has discontinued its morphometric identification service. Other university and state labs still test for Africanized genetics.

Related reading

Sources

  • Mississippi State University Extension, “Africanized honey bees not established in Mississippi” (2025): https://extension.msstate.edu/news/feature-story/2025/africanized-honey-bees-not-established-mississippi
  • UF/IFAS EDIS ENY-147, “Differences Between European and African Honey Bees”: https://ask.ifas.ufl.edu/publication/IN784
  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee”: https://edis.ifas.ufl.edu/publication/IN790
  • UF/IFAS EDIS ENY-170, “Living with the African Honey Bee”: https://ask.ifas.ufl.edu/publication/IN1205/pdf
  • Ohio State University BYGL, “Myths and facts – Africanized honey bees” (2024): https://bygl.osu.edu/node/2431
  • Sylvester & Rinderer, “Fast Africanized Bee Identification System (FABIS) Manual,” USDA ARS: https://www.ars.usda.gov/ARSUserFiles/60500500/PDFFiles/101-200/185-Sylvester–Fast%20Africanized%20Bee%20Identification.pdf
  • USDA ARS Carl Hayden Bee Research Center, “Africanized Bee Identification”: https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/docs/africanized-honey-bees/africanized-bee-identification/
  • USDA ARS Carl Hayden Bee Research Center, “Africanized Honey Bees Overview”: https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/docs/africanized-honey-bees/africanized-honey-bees-overview/
  • Michigan State University Extension, “Diagnostic labs and services for beekeepers” (2025): https://www.canr.msu.edu/news/diagnostic-labs-and-services-for-beekeepers
  • Kono & Kohn, “Range and Frequency of Africanized Honey Bees in California (USA),” PLOS ONE (2015): https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137407
  • USDA ARS, “Africanized Honey Bees: The March North Has Slowed,” Agricultural Research (1996): https://agresearchmag.ars.usda.gov/1996/mar/forum/
  • USDA Forest Service MTDC, “Working Safely in Areas With Africanized Honey Bees”: https://www.fs.usda.gov/t-d/pubs/htmlpubs/htm00672313/index.htm
  • University of Arizona Extension, “Feral Honeybees” (Backyard Gardener #119): https://extension.arizona.edu/sites/extension.arizona.edu/files/attachment/FeralHoneybees.pdf
  • NC State Extension, “Africanized Honey Bees: Prevention and Control”: https://content.ces.ncsu.edu/africanized-honey-bees-prevention-and-control

Killer Bee Swarm Season: When Africanized Bees Swarm and What to Do

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A cluster of thousands of bees hanging from a branch looks alarming, and in parts of the southern United States people immediately wonder whether it’s a “killer bee swarm.” The surprising answer from extension entomologists is that a swarm, Africanized or not, is usually the calmest stage of a honey bee colony’s life. The real risk comes later, once the bees move in somewhere and start defending a nest.

This guide explains what swarming is, when swarm season happens, why Africanized honey bees swarm so much more often than European bees, and what to do if a swarm shows up on your property. It’s part of our Killer Bees 101 guide.

What is a honey bee swarm?

Swarming is how a honey bee colony reproduces. University of Florida (UF/IFAS) entomologists describe it this way: when a colony grows crowded, roughly 30 to 60 percent of the bees leave with the old queen to look for a new home. The bees left behind raise a new queen and carry on in the original nest.

The departing bees don’t fly straight to a new home. They usually settle into a temporary cluster on a branch, fence, eave, or even a parked vehicle while scout bees search for a cavity. According to the USDA Agricultural Research Service (ARS) Carl Hayden Bee Research Center in Tucson, exposed swarms like this are vulnerable and typically leave within 24 to 48 hours. If they can’t find a suitable site, they may fly several miles and cluster again.

Swarming vs. absconding

Africanized honey bees have a second way of moving that European bees rarely use. Absconding is when the entire colony abandons its nest, brood and all. UF/IFAS notes that African-derived bees abscond frequently during times of dearth (little nectar or pollen) or after repeated disturbance, while the behavior is unusual in European bees.

So a “swarm” in Africanized territory might be a reproductive swarm or an absconding colony on the move. To a homeowner, they look the same: a cluster of bees that isn’t attached to comb.

Why Africanized bees swarm so often

The behavioral gap is large:

European honey bee Africanized honey bee
Swarms per year About 1 to 3 (UF/IFAS); USDA ARS says typically once every 12 months 10 or more (UF/IFAS); USDA ARS says as often as every six weeks during swarm season, sometimes with several swarms each time
Swarm size Larger Smaller
Nest cavity needed About 10 gallons About 1 to 5 gallons
Absconding Rare Common

Sources: UF/IFAS EDIS ENY-147 and EENY-429; USDA ARS Carl Hayden Bee Research Center.

UF/IFAS explains that Africanized colonies evolved in tropical regions where food is available much of the year, so they don’t build up big honey reserves. Instead, they grow fast, split often, and spread. Their smaller swarms fit into much smaller spaces, which is why they turn up in water meter boxes, cement blocks, old tires, overturned flower pots, and barbecue grills. You can read more about those behavioral differences in Africanized vs. European Honey Bees.

When is killer bee swarm season?

There isn’t one national date, because swarming follows the bloom. University of Arizona Extension explains that as spring days lengthen and plants produce new pollen and nectar, colonies raise more brood and become overcrowded, which triggers swarming. Swarming is common in spring and continues through the year while pollen and nectar can support growing colonies, so local rainfall and bloom drive the timing.

A few regional examples from public agencies:

  • Florida: UF/IFAS Solutions for Your Life identifies March to July as swarming season and recommends inspecting your property weekly during that window.
  • Arizona’s low desert: University of Arizona Extension notes two main nectar flows each year, one after the winter rains and one after the summer monsoons. Its homeowner guidance says to watch for swarms during spring and summer in particular.
  • San Diego County, California: the county agriculture department, which considers the entire county colonized by Africanized bees, says bees are most active in spring and fall and advises extra caution then.

In northern states where Africanized bees aren’t established, ordinary honey bee swarming is concentrated in spring and early summer. Those swarms are European bees, and they’re just as gentle at the swarm stage. (See Are There Killer Bees in Ohio? for the Midwest picture.)

Are killer bee swarms dangerous?

Generally, no. USDA ARS states plainly that swarms are generally docile regardless of type, because a swarm has no brood, stored food, or nest to protect. ARS adds that Africanized honey bees do not fly out in angry swarms to attack random victims; stinging incidents happen when a nest, not a swarm, is disturbed.

That said, extension specialists give three important cautions:

  1. You can’t always tell a swarm from a new nest. UF/IFAS advises never approaching a swarm, because you can’t be sure it’s only a swarm and not a colony that has already started building comb.
  2. Swarms don’t stay swarms. If a swarm moves into your wall, shed, or meter box, it becomes an established colony. UF/IFAS warns that a small, calm colony left alone “can become larger and more aggressive as it gets established.”
  3. Provocation changes everything. Throwing things at a swarm, spraying it, or hosing it down can trigger defense.

How to tell a swarm from an established colony

University of Arizona Extension offers practical clues:

  • A cluster that appears suddenly on a branch, wall, or other surface is most likely a resting swarm.
  • Swarming bees won’t have yellow or orange pollen loads on their hind legs.
  • Swarms won’t be streaming in and out of a cavity. If you see a steady line of bees flying into a gap in siding, a hole in the ground, or a valve box, there’s a colony inside.

What to do if a swarm lands on your property

  1. Keep people and pets away. Give the cluster a wide berth and bring animals indoors. Extension guidance from UF/IFAS stresses that pets tethered or penned near bees can’t escape if the bees become defensive. Our guide to protecting pets and livestock from killer bees covers this in detail.
  2. Don’t spray, swat, burn, or hose it. University of Arizona Extension specifically warns never to shoot, throw rocks at, pour gasoline on, burn, or treat bee colonies with pesticides yourself.
  3. Hold off on noisy equipment. Texas A&M’s apiary inspection service lists mower, weed-eater, tractor, and chain saw vibration among the common triggers for Africanized bees.
  4. Call for help, especially in Africanized areas. NC State Extension recommends contacting a local beekeeper about swarms. In states where Africanized bees are established, Florida’s agriculture department recommends that feral colonies near people be removed by a registered beekeeper or trained pest control operator, or eradicated by a licensed operator.
  5. Watch where it goes. If the swarm leaves within a day or two, great. If bees start flying in and out of a spot on your house, treat it as an established colony and get professional help.

If bees do start stinging, don’t stand still. Read What to Do If Killer Bees Attack before swarm season so the steps are already familiar.

Bee-proof before swarm season starts

The best time to prevent a colony in your wall is before scout bees find the gap. UF/IFAS and NC State Extension both recommend:

  • Seal gaps larger than 1/8 inch in walls and around chimneys, pipes, and plumbing.
  • Screen openings such as vents, rain spouts, and water meter boxes with 1/8-inch hardware cloth.
  • Clear junk piles, old tires, overturned flower pots, inverted buckets, and abandoned equipment.
  • Fill rodent and animal burrows in the ground (University of Arizona Extension).
  • Inspect regularly. UF/IFAS suggests weekly checks during swarming season; University of Arizona Extension suggests at least monthly checks around the house and yard.

Frequently asked questions

How long will a killer bee swarm stay in one place?

USDA ARS says exposed swarms typically leave within 24 to 48 hours once scouts find a new home. If a cluster is still there after several days, or bees are going in and out of a gap, they may have moved in.

Do Africanized bees swarm more than regular honey bees?

Yes, much more. UF/IFAS reports European colonies swarm about one to three times a year, while African-derived colonies can swarm 10 or more times. USDA ARS says Africanized colonies can swarm as often as every six weeks during swarm season.

Will a swarm attack me if I walk by?

It’s unlikely. Swarms are generally docile because they have no nest to defend. Still, keep your distance and don’t disturb the cluster, since you can’t be certain it hasn’t started a nest.

What time of year do killer bees swarm?

Mainly in spring, continuing into summer and sometimes fall wherever bloom continues. Florida’s swarming season runs roughly March to July, and Arizona’s low desert sees activity after both the winter rains and the summer monsoons.

Should I kill a swarm with insecticide?

Extension services advise against doing it yourself. Call a beekeeper or a trained pest control operator. A swarm will often move on by itself within a day or two.

Related reading

Sources

  • USDA ARS Carl Hayden Bee Research Center, “Africanized Honey Bees Overview”: https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/docs/africanized-honey-bees/africanized-honey-bees-overview/
  • UF/IFAS EDIS ENY-147, “Differences Between European and African Honey Bees”: https://ask.ifas.ufl.edu/publication/IN784
  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee”: https://edis.ifas.ufl.edu/publication/IN790
  • UF/IFAS EDIS ENY-170, “Living with the African Honey Bee”: https://ask.ifas.ufl.edu/publication/IN1205/pdf
  • UF/IFAS Solutions for Your Life, “Africanized Honey Bees”: https://sfyl.ifas.ufl.edu/natural-resources/africanized-honey-bees/
  • University of Arizona Extension AZ1846, “Wild Honey Bees in Community Environments”: https://extension.arizona.edu/sites/default/files/2024-08/az1846-2020.pdf
  • University of Arizona Extension AZ2046, “Monofloral Honeys”: https://extension.arizona.edu/sites/default/files/2024-08/az2046-2023.pdf
  • University of Arizona Extension, “They are called Africanized Honey Bees”: https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/195020a.pdf
  • NC State Extension, “Africanized Honey Bees: Prevention and Control”: https://content.ces.ncsu.edu/africanized-honey-bees-prevention-and-control
  • Texas Apiary Inspection Service, “Africanized Bees”: https://txbeeinspection.tamu.edu/public/africanized-bees/
  • County of San Diego Department of Agriculture, Weights and Measures, “Africanized Honey Bees: How to Avoid”: https://www.sandiegocounty.gov/content/dam/sdc/common_components/images/awm/Docs/ahb_avoid.pdf

Where Do Killer Bees Live? The U.S. Range Explained

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Africanized honey bees, the bees nicknamed “killer bees,” are established across the southern edge of the United States. They have not moved into the colder northern states, and the scientific explanation is mostly climate. This post covers where they live, how they got there, and why the spread slowed. It’s part of our Killer Bees 101 guide.

The short answer

As of the most recent extension summary we found (University of Florida, citing data through 2012), Africanized honey bees had been found in Texas, California, New Mexico, Arizona, Oklahoma, Louisiana, Arkansas, Alabama, and Florida. A 2004 USDA Agricultural Research Service report also lists southern Nevada, plus Puerto Rico and the U.S. Virgin Islands.

“Found in” and “established everywhere in” are different things. In several of those states the bees occupy only the southern counties. Florida’s extension service, for example, describes them as established in the southern half of the state.

How the range grew

  • 1990: The first Africanized swarm in the U.S. was found on October 15, 1990, in a USDA trap outside Hidalgo, Texas.
  • 1993: First seen in Arizona, according to University of Arizona Extension. By 1997 they had reached Yavapai County in central Arizona, and today they’re recorded statewide.
  • 1996: USDA reported them in parts of Texas, Arizona, New Mexico, California, Puerto Rico, and St. Croix.
  • 2001–2003: Florida documented them near the Port of Tampa in 2001, and by 2003 they had established colonies around Tampa, according to UF/IFAS.
  • 2004: USDA listed five states (Texas, Arizona, New Mexico, southern California, and Nevada) plus Puerto Rico and the U.S. Virgin Islands.
  • 2006: Texas had detected them in 163 of its 254 counties, according to the Texas Apiary Inspection Service.
  • 2012: Nine states, per the University of Florida summary above.

The full backstory, from Brazil in the 1950s to the Texas border, is in The History of Killer Bees.

Why they stopped moving north

In South and Central America, Africanized bees spread an estimated 200 to 300 miles a year, according to UF/IFAS. In the U.S. the advance slowed sharply, and researchers point to climate.

Cold winters

These bees come from tropical and subtropical Africa, and they store less honey than European bees. UF/IFAS says plainly that they don’t survive temperate climates as well as European bees do. UF/IFAS and University of Arizona Extension both describe them as established only below about 34° north latitude. For reference, that line runs roughly through Los Angeles, just north of Phoenix, central New Mexico, north Texas near the Oklahoma line, southern Arkansas, and the northern parts of Mississippi, Alabama, and Georgia. In the southern hemisphere they also stalled near 32° south. For the Midwest angle, including Michigan and Indiana, see Are Killer Bees Moving North?

Rainfall

In 2004, USDA ARS entomologist José Villa reported a strong correlation between heavy, even rainfall (more than 55 inches a year, spread through the year) and an almost complete barrier to their spread. He was careful to say this was a correlation, not a proven cause, but it helps explain why parts of the humid Southeast filled in more slowly than the dry Southwest.

Competition and hybridization

USDA noted in 1996 that interbreeding with resident European bees, diseases, parasites, and cold weather may all be slowing the advance. A strong population of European bees, kept gentle by beekeepers who requeen regularly, may be an area’s best buffer.

What about the northern states?

Africanized bees are not established in the Midwest or Northeast. Ohio State University extension specialists have said there are no Africanized bees in Ohio. In 2024 OSU tested a suspected “killer bee” colony from southwest Ohio and found it was an ordinary western honey bee colony. We cover the Ohio question in detail in Are There Killer Bees in Ohio?.

So how do people up north run into them? Occasionally a swarm hitches a ride on cargo, or a beekeeper buys package bees or queens from a southern supplier. If you’re a northern beekeeper ordering queens or packages, ask the supplier where the stock was raised and how they keep it European. A single stray colony isn’t an established population, and a northern winter is hard on bees adapted to the tropics.

Will climate change push them north?

Possibly, and it’s reasonable to ask. If the cold limit is real, milder winters could let the range creep north over time. We found no current federal forecast or 2020s survey that puts numbers on it, so we won’t guess. What we can say is that the bees’ advance has been slow and uneven, and decades of watching have not shown them sweeping into northern states.

What this means for you

  • In the Southwest, Texas, or southern Florida: Treat every wild honey bee colony as potentially Africanized. Bee-proof your property, check before mowing, and learn what to do if bees attack.
  • In the North: Your stinging-insect problems are much more likely to be yellowjackets, paper wasps, and hornets than Africanized bees. A defensive honey bee colony in a wall still deserves professional help. See Bee & Wasp Removal.
  • If you buy honey labeled “killer bee honey”: It has to come from a region where these bees actually live. See What Is Killer Bee Honey?.

Frequently asked questions

Which states have killer bees?

University of Florida’s summary (data through 2012) lists Texas, California, New Mexico, Arizona, Oklahoma, Louisiana, Arkansas, Alabama, and Florida. USDA also lists southern Nevada, Puerto Rico, and the U.S. Virgin Islands.

Are killer bees in every part of those states?

No. In many states they are limited to southern areas. Arizona and much of Texas are the most heavily Africanized.

How far north can killer bees live?

They’re currently established below roughly 34° north latitude, according to UF/IFAS and University of Arizona Extension.

When did killer bees arrive in the U.S.?

October 15, 1990, near Hidalgo, Texas, according to USDA ARS.

Is there an official current range map?

USDA ARS has published county-level spread maps, but we did not find a federal map updated in the 2020s. Check your state’s department of agriculture or apiary program for local status.

Related reading

Sources

  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee” (distribution section): https://edis.ifas.ufl.edu/publication/IN790
  • UF/IFAS EDIS ENY-170, “Living with the African Honey Bee”: https://ask.ifas.ufl.edu/publication/IN1205/pdf
  • USDA ARS, “The Latest Research on Africanized Honey Bees” (2004): https://www.ars.usda.gov/news-events/news/research-news/2004/the-latest-research-on-africanized-honey-bees/
  • USDA ARS, “Africanized Honey Bees: The March North Has Slowed” (1996): https://agresearchmag.ars.usda.gov/1996/mar/forum/
  • Texas Apiary Inspection Service, “Africanized Bees”: https://txbeeinspection.tamu.edu/public/africanized-bees/
  • University of Arizona Extension, “Feral Honeybees” (Backyard Gardener #119, 2023): https://extension.arizona.edu/sites/extension.arizona.edu/files/attachment/FeralHoneybees.pdf
  • University of Arizona Extension AZ2011, “Honeybee Basic Biology”: https://www.extension.arizona.edu/publication/honeybee-series-honeybee-basic-biology
  • Ask Extension (Ohio State), “Have Africanized bees entered Ohio?”: https://ask.extension.org/kb/faq.php?id=265942
  • Ohio State University BYGL, “Myths and facts – Africanized honey bees”: https://bygl.osu.edu/node/2431

Are There Killer Bees in Ohio? What NW Ohio Residents Should Know

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We get this question every summer, usually right after a news clip about Arizona or Texas: are there killer bees in Ohio? The short answer is no. Africanized honey bees are not established here. That doesn’t mean every sting around Fostoria is harmless, so here’s what Ohio residents actually need to know. For the national picture, see our Killer Bees 101 guide and Where Do Killer Bees Live?.

What the experts say about Ohio

Ohio State University is the authority here. In a 2015 Ask Extension answer, an OSU extension specialist answered a Summit County resident directly: “We don’t have ‘Africanized’ bees in Ohio. They are currently only in the southernmost states.” A second expert in the same thread added a fair caveat. There is likely some small degree of Africanization in honey bee populations across the U.S., but Africanized bees are not reported in Ohio.

That fits the science on range. UF/IFAS and University of Arizona Extension describe Africanized bees as established only below about 34° north latitude. Fostoria sits around 41° north, roughly 500 miles north of that line, and gets real Ohio winters.

The 2024 “killer bee” scare in southwest Ohio

In July 2024, OSU’s Department of Entomology got a call from a Hamilton County beekeeper who was sure one of his colonies was Africanized. It was noticeably meaner than his others. He netted the hive, mailed in a few dozen bees, and destroyed the colony before the results came back.

OSU used the USDA FABIS method, which starts with forewing length. The ten bees averaged 9.27 mm, above the 9.001 mm cutoff for Africanized bees. The bees were ordinary western honey bees. What he had was a defensive colony, which happens in Ohio for ordinary reasons. Researchers published the result as “Myths and facts – Africanized honey bees.”

The lesson for Ohio beekeepers is to test before you act. A hot colony may be queenless, hungry, harassed by skunks, or just carrying cranky genetics. Requeening with a gentle queen is the standard fix.

So what’s actually stinging people in Northwest Ohio?

Across Northwest Ohio, including Seneca, Hancock, Wood, and Sandusky counties, most painful late-summer stings come from wasps, not honey bees.

Yellowjackets

OSU’s Ohioline fact sheet notes that the German yellowjacket arrived in Ohio in 1975 and is now the dominant species. Yellowjackets nest in old rodent burrows, mulch beds, and wall voids. A nest can reach 4,000 to 5,000 workers by late summer. From August to October they switch to sweets, which is when they show up at cookouts. Unlike honey bees, they can sting repeatedly. Mowing over a ground nest is the classic way to get hurt. For a side-by-side comparison, see Killer Bees vs. Murder Hornets, Yellowjackets, and Wasps.

Hornets and paper wasps

Bald-faced hornets build the gray paper footballs you see in trees and on eaves. Paper wasps build open, umbrella-shaped combs under decks and soffits. Both defend their nests.

Honey bees in walls

European honey bees do move into Ohio homes: wall cavities, soffits, chimneys. They’re usually calm, but a colony in a wall shouldn’t just be sprayed and sealed in. University of Arizona Extension advises that once a colony is removed from a void, the space should be cleaned out completely and the entrances sealed, or new swarms will move back in. Comb and honey left in a wall can also attract pests. A live removal followed by a proper cleanup is the right approach.

How to tell a honey bee from a yellowjacket

OSU’s description is the most useful one we know:

  • Honey bees are fuzzy, golden-brown, with flattened, hairy hind legs for carrying pollen. They often fan their wings out slightly while feeding.
  • Yellowjackets are hard, shiny, mostly hairless, bright yellow and black, and fold their wings lengthwise at rest.

If it’s crawling into a hole in your lawn or a gap in your siding in September, it’s probably yellowjackets.

When to call for help

You don’t need to worry about killer bees in Ohio, but you should take any nest seriously if it’s near a door, play area, or mowing path, or if anyone in the house is allergic.

For honey bee swarms and colonies in walls or chimneys, look for a local beekeeper who does live removals. Many county beekeeping associations keep swarm-call lists.

For yellowjacket, hornet, and wasp nests, our sister service covers Fostoria and the surrounding counties: Northwest Ohio Wasp Removal.

More detail on both is on our Bee & Wasp Removal page.

If you’re stung

Ohio State’s guidance on yellowjacket stings is to ice the area in 10-minute stretches and take an antihistamine for swelling and itching if needed. Get medical attention if you’ve been stung more than ten times or stung in the mouth or around the eyes. Get emergency care right away for trouble breathing or swallowing, throat tightness, confusion, or fainting. Our sting guide explains how honey bee stings differ, including why you should scrape a honey bee stinger out quickly.

Frequently asked questions

Are there killer bees in Ohio?

No. Ohio State extension experts state that Africanized honey bees are not established in Ohio. In a 2024 test of a suspected colony, OSU found ordinary western honey bees.

Could killer bees reach Ohio someday?

Their spread in the U.S. has stalled around 34° north, and they don’t survive temperate winters as well as European bees. A stray swarm could arrive on a truck or with shipped bees, but that isn’t an established population. We know of no forecast that puts them in Ohio.

My bees are aggressive. Should I kill the colony?

No, not before testing. Contact the Ohio Department of Agriculture apiary program or OSU. Most hot colonies in Ohio are just defensive European bees, and requeening usually fixes it.

What stinging insect causes the most trouble in NW Ohio?

In late summer, yellowjackets, especially the German yellowjacket, which OSU calls the dominant species in Ohio.

Who removes bees and wasps near Fostoria?

For honey bees, a local beekeeper who does live removals (county beekeeping associations often keep swarm lists). For yellowjackets and hornets, see ohiowaspremoval.com.

Related reading

Sources

  • Ask Extension (Ohio State), “Have Africanized bees entered Ohio?” (2015): https://ask.extension.org/kb/faq.php?id=265942
  • Ohio State University BYGL, “Myths and facts – Africanized honey bees” (Oct 8, 2024): https://bygl.osu.edu/node/2431
  • Ohio State University Ohioline HYG-2075, “Yellowjackets”: https://ohioline.osu.edu/factsheet/HYG-2075-11
  • University of Arizona Extension AZ1846, “Wild Honey Bees in Community Environments”: https://extension.arizona.edu/sites/default/files/2024-08/az1846-2020.pdf
  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee”: https://edis.ifas.ufl.edu/publication/IN790
  • University of Arizona Extension AZ2011, “Honeybee Basic Biology”: https://www.extension.arizona.edu/publication/honeybee-series-honeybee-basic-biology

What Are Killer Bees? The Science Behind Africanized Honey Bees

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“Killer bee” is a movie name for a real insect. The bee people mean is the Africanized honey bee, and the science is a lot more interesting than the horror version. This post covers what the bee actually is, how it differs from the honey bees most Americans know, and why the nickname stuck. It’s one part of our larger guide, Killer Bees 101, which pulls the whole topic together. For the most common misconceptions, see Why Are They Called Killer Bees? 10 Myths vs. Facts.

The short answer

A killer bee is a honey bee. It is the same species as the bees beekeepers keep across the country, Apis mellifera. The difference is ancestry and behavior, not the bee’s size or a stronger venom.

University of Florida entomologists explain that African and European honey bees are the same species but different subspecies. The African subspecies at the root of the story is Apis mellifera scutellata, native to sub-Saharan Africa. In the Americas, “Africanized” refers to hybrids between that bee and the European subspecies beekeepers brought over centuries earlier.

So when someone says “killer bees,” they mean honey bees with a large share of African ancestry. They make honey, pollinate crops, and live in colonies with a queen, workers, and drones like any other honey bee. (Does their honey taste different? See Does Killer Bee Honey Taste Different?)

Where the “killer” label came from

The nickname comes from how hard these colonies defend the nest. The bee itself has nothing special about it.

UF/IFAS puts the numbers side by side. A disturbed European honey bee colony may send out 10 to 20 guard bees in response to a disturbance up to about 20 feet away. A disturbed Africanized colony may send several hundred, in response to a disturbance up to about 120 feet away. A European colony usually calms down within an hour or two. An Africanized colony may stay defensive for days. A disturbed European colony might deliver 10 to 20 stings. An Africanized colony can deliver 100 to 1,000.

That is the whole story behind the name. The danger is volume. A large number of stings at once can seriously hurt or kill a person or an animal, and pets or livestock that are tied up or penned can’t get away. We cover the medical side in How Dangerous Is a Killer Bee Sting?.

UF/IFAS also points out that “defensive” is the more accurate word than “aggressive.” These bees don’t go hunting for people. They react when someone gets too close to the nest. USDA’s Carl Hayden Bee Research Center in Tucson says it plainly: Africanized honey bees do not fly out in angry swarms to attack random victims. Stinging incidents happen when the nest itself is disturbed.

Same venom, different response

People are often surprised that Africanized venom is no stronger than European honey bee venom. UF/IFAS states this directly, and Texas A&M’s Apiary Inspection Service says the same thing: the venom is the same, and only the behavior can differ.

The University of Florida’s species profile goes further. Africanized bees are slightly smaller than European bees, so each one probably delivers a slightly smaller dose of venom. When deaths happen, it’s usually because of the number of stings, unless the person is allergic, in which case even one sting can be life-threatening.

Can you tell them apart by looking?

No. Africanized workers are roughly 10 percent smaller than European workers, according to UF/IFAS, but you can’t see that difference by eye. Labs identify them by measuring wing and body parts (morphometrics) or through genetic testing. We explain how in Africanized vs. European Honey Bees: How to Tell the Difference.

Other ways Africanized bees behave differently

Defensiveness gets the headlines, but beekeepers also notice these traits:

They swarm far more often

USDA ARS notes that a European colony typically swarms about once a year. An Africanized colony may swarm as often as every six weeks during swarm season. UF/IFAS puts it at 10 or more times a year.

They nest in small, odd places

Africanized colonies are smaller and accept much smaller cavities, often 1 to 5 gallons compared with the roughly 10-gallon cavity a European colony prefers. USDA lists water meter boxes, cement blocks, old tires, overturned flower pots, utility poles, junk piles, and house eaves. That’s why people run into them by accident.

They abscond

When food runs short or the nest keeps getting disturbed, an Africanized colony may abandon the nest entirely. European colonies rarely do this.

They store less honey

USDA and University of Arizona Extension both note that Africanized colonies tend to store less honey than European colonies. That makes sense for a bee that evolved where flowers bloom most of the year. It matters for honey, and we cover it in What Is Killer Bee Honey?.

They develop faster

UF/IFAS lists development times of about 14 days for an Africanized queen versus 16 for a European queen, and 19 to 20 days for an Africanized worker versus 21. A queen that hatches first can kill her rivals, which helps African genetics take over a mixed population.

Why a beekeeper cares

To a beekeeper, the Africanized honey bee is a management problem more than a monster. Colonies can be worked, and in much of South and Central America they are the standard honey bee. UF/IFAS notes that some South American countries are among the world’s leading honey producers largely because of African-derived bees. Working them takes heavier protective gear, more smoke, more space between hives, and a lot of respect.

For everyone else, the takeaways are simple. Leave colonies alone, don’t try to remove a nest yourself, and know what to do if bees attack. If you live in the North, also know that these bees are not established in your state. We look at that in Where Do Killer Bees Live? and Are There Killer Bees in Ohio?.

Where they came from, briefly

The African bees were brought to Brazil in 1956 to breed a honey bee better suited to the tropics. In 1957 some escaped quarantine, and their descendants spread across South and Central America and reached Texas in 1990. The full timeline is in The History of Killer Bees.

Frequently asked questions

Are killer bees a different species from regular honey bees?

No. Africanized and European honey bees are both Apis mellifera. They are different subspecies (or hybrids of subspecies), which is why they interbreed freely.

Is killer bee venom stronger?

No. UF/IFAS and Texas A&M both state that the venom is the same. The danger comes from the number of bees that respond and the number of stings.

Do killer bees chase people for no reason?

No. They defend the nest. Stinging incidents start when someone disturbs the colony, often without knowing it’s there, for example by running a mower or trimmer near a hidden nest. Once triggered, they may pursue a person a long way.

Are swarms of killer bees dangerous?

Swarms of any honey bee are generally docile because they have no brood or stored honey to protect, according to USDA ARS. Still, keep your distance, because you can’t always tell a resting swarm from a newly established colony.

Do killer bees make honey?

Yes. They are honey bees and make honey from flower nectar. See our Killer Bee Honey guide.

Related reading

Sources

  • USDA ARS Carl Hayden Bee Research Center, “Africanized Honey Bees Overview”: https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/docs/africanized-honey-bees/africanized-honey-bees-overview/
  • UF/IFAS EDIS ENY-147, “Differences Between European and African Honey Bees”: https://ask.ifas.ufl.edu/publication/IN784
  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee”: https://edis.ifas.ufl.edu/publication/IN790
  • UF/IFAS Solutions for Your Life, “Africanized Honey Bees”: https://sfyl.ifas.ufl.edu/natural-resources/africanized-honey-bees/
  • Texas Apiary Inspection Service (Texas A&M), “Africanized Bees”: https://txbeeinspection.tamu.edu/public/africanized-bees/
  • University of Arizona Extension AZ2011, “Honeybee Basic Biology”: https://www.extension.arizona.edu/publication/honeybee-series-honeybee-basic-biology
  • USDA ARS, “Africanized Honey Bees: The March North Has Slowed” (1996): https://agresearchmag.ars.usda.gov/1996/mar/forum/

How Dangerous Is a Killer Bee Sting?

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A single sting from an Africanized “killer” bee hurts exactly as much as a sting from any other honey bee, and it’s no more toxic. What makes these bees dangerous is how many of them sting at once. This guide explains the venom, the sting numbers that matter, and the warning signs that mean you need help. It’s part of Killer Bees 101. If you want the escape plan first, read What to Do If Killer Bees Attack.

This page is general information, not medical advice. In an emergency, call 911.

Is killer bee venom stronger?

No. This is one of the most common misunderstandings, and extension services are clear about it:

  • UF/IFAS: “The venom of the Africanized honey bee is no more potent than that of the European honey bee.”
  • Texas A&M’s Apiary Inspection Service: “The venom is the same.”
  • University of Florida’s species profile goes a step further. Africanized bees are slightly smaller, so each one “probably deliver[s] a comparatively smaller dose of venom.” Human deaths are “usually a result of the number of stings received rather than an increased potency.”

The real issue: sting count

Here’s how UF/IFAS compares a disturbed colony of each type:

European honey bee Africanized honey bee
Guard bees that respond About 10–20 Several hundred
Stings from a disturbed colony About 10–20 About 100–1,000
How long the colony stays agitated 1–2 hours Possibly days

An Africanized colony may also chase a person 400 yards or more. A big part of surviving an attack is simply limiting how many stings you take, which is why the escape steps matter so much.

How many stings can kill a person?

There are two very different dangers here.

1. Allergy: one sting can be enough

For someone with a severe allergy, a single sting from any bee or wasp can trigger anaphylaxis. UF/IFAS notes that for an allergic victim, one sting can cause death. Mayo Clinic says anaphylaxis affects a small percentage of people who are stung and usually begins within 15 minutes to an hour.

2. Toxic envenomation: the numbers game

For people who aren’t allergic, the danger is the total venom dose. Extension estimates:

  • UF/IFAS (ENY-147): a fatal venom dose “normally would take about 10 stings per pound of body weight” from either type of honey bee.
  • UF/IFAS (ENY-170): there is a risk of toxic envenomation after about 5–10 stings per pound of body weight.

For a 150-pound adult, that’s roughly 750 to 1,500 stings, a range a defending Africanized colony can reach. For a 40-pound child it’s about 200 to 400. That’s why children, older adults, and people who can’t move quickly are at the highest risk. These are rough population estimates, not a safe limit. Health, age, and where the stings land all matter.

Medical trouble starts far below lethal numbers. Mayo Clinic says that more than a dozen stings can make a person quite sick. University of Arizona Extension advises seeing a doctor after more than 15 stings.

Normal reaction vs. emergency

Mayo Clinic describes three levels of reaction:

Mild

Sharp burning pain, a red welt, and some swelling at the sting. It usually fades within a few hours.

Moderate

More redness and swelling that grows over a day or two and can last up to a week. UF/IFAS notes that swelling around the sting is normal and doesn’t by itself mean an allergy.

Severe (anaphylaxis): call 911

Watch for:
– Trouble breathing, or tightness in the chest or throat
– A swollen tongue or trouble swallowing
– Hives or itching spreading away from the sting site
– Nausea, vomiting, dizziness, a rapid weak pulse, or fainting

If the person has a prescribed epinephrine auto-injector, Mayo Clinic says to use it right away and then call 911.

Multiple stings

Mayo Clinic lists nausea, vomiting, diarrhea, fever, and lightheadedness after many stings. It recommends immediate care for multiple stings in children, older adults, and anyone with heart or breathing problems, even without allergy symptoms.

First aid for honey bee stings

  1. Get away from the bees first. Treating stings while you’re still near the colony gets you stung more.
  2. Scrape stingers out quickly. Honey bee stingers are barbed, and the venom sac keeps pumping after the bee is gone. UF/IFAS says the method doesn’t matter as much as speed. A fingernail or credit-card edge works well.
  3. Wash with soap and water to prevent infection.
  4. Ice to reduce pain and swelling.
  5. Watch closely for at least an hour. Mayo Clinic says anaphylaxis usually begins within 15 minutes to an hour. Keep a closer eye on children and on anyone who got many stings.

Honey bees vs. wasps: why the stinger matters

A worker honey bee can sting only once. The barbed stinger catches in skin, tears free, and the bee dies soon after. Yellowjackets don’t lose their stinger, and Ohio State’s yellowjacket fact sheet notes that they can sting repeatedly. In places like Northwest Ohio, where Africanized bees aren’t established (see Are There Killer Bees in Ohio?), a ground nest of yellowjackets is the more likely source of multiple stings.

If you’ve had a bad reaction before

Mayo Clinic reports that people who had a severe reaction to a sting have, on average, a 50 percent chance of anaphylaxis the next time. Ask a doctor about carrying epinephrine and about allergy shots (venom immunotherapy).

Frequently asked questions

Does a killer bee sting hurt more than a regular bee sting?

No. It’s the same venom from a slightly smaller bee.

How many killer bee stings does it take to kill someone?

For someone who isn’t allergic, extension estimates put the toxic range at about 5–10 stings per pound of body weight. For a severely allergic person, one sting from any bee can be life-threatening.

When should I go to the doctor after bee stings?

Right away for any sign of anaphylaxis. Also promptly after more than about a dozen to 15 stings, or for any child, older adult, or person with heart or lung problems who has multiple stings.

Do killer bees die after stinging?

Yes. Like all worker honey bees, they lose the barbed stinger and die soon after.

Is swelling a sign of allergy?

Swelling at the sting site is normal. Swelling, hives, or breathing trouble away from the sting site suggests a systemic reaction that needs emergency care.

Related reading

Sources

  • UF/IFAS EDIS ENY-147, “Differences Between European and African Honey Bees”: https://ask.ifas.ufl.edu/publication/IN784
  • UF/IFAS EDIS ENY-170, “Living with the African Honey Bee”: https://ask.ifas.ufl.edu/publication/IN1205/pdf
  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee”: https://edis.ifas.ufl.edu/publication/IN790
  • UF/IFAS Solutions for Your Life, “Africanized Honey Bees”: https://sfyl.ifas.ufl.edu/natural-resources/africanized-honey-bees/
  • Texas Apiary Inspection Service, “Africanized Bees”: https://txbeeinspection.tamu.edu/public/africanized-bees/
  • University of Arizona Extension, “They are called Africanized Honey Bees”: https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/195020a.pdf
  • Mayo Clinic, “Bee sting – Symptoms and causes” (Oct 24, 2024): https://www.mayoclinic.org/diseases-conditions/bee-stings/symptoms-causes/syc-20353869
  • Ohio State University Ohioline HYG-2075, “Yellowjackets”: https://ohioline.osu.edu/factsheet/HYG-2075-11

What to Do If Killer Bees Attack

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Most people will never be attacked by Africanized honey bees. If you live, work, or travel where they’re established, though, the right response is simple, and it’s the opposite of what instinct tells you. Read this once, share it with your family, and you’ll know what to do. It’s part of our Killer Bees 101 guide.

The one-line version

Run. Cover your face. Get inside a car or building. Don’t stop, don’t swat, and don’t jump in water.

Texas A&M’s Apiary Inspection Service teaches it as A-C-E: Alert others, Cover your head and face without blocking your vision, and Exit into a car or house immediately.

Why running works

An Africanized colony defends the nest, not you personally. UF/IFAS explains that once stinging starts, you’re too close to the nest and need to leave the area right away. These bees do pursue. UF/IFAS says they may follow an intruder 400 yards or more, so you need real distance or a real barrier, not a few steps back.

Step by step

1. Run immediately, in a straight line

Don’t stop to figure out where the bees came from. UF/IFAS advises running in a straight line to shelter. UF’s species profile adds that running through tall grass or small trees can help break up the pursuing bees.

2. Protect your face and airways

Pull your shirt up over your nose and mouth as you run. Bees target the head, eyes, and breathing openings, and covering them limits stings where they do the most harm. University of Arizona Extension says to cover your head as much as you can without slowing down.

3. Get inside an enclosed space

A car, house, shed, or any building with a door. UF/IFAS notes that a few bees will probably follow you in, but most will stay outside. Once inside, move away from the door and deal with the few that got in.

4. Don’t swat or flail

Swatting and rapid movements agitate bees further. University of Arizona Extension also notes that each sting releases an alarm pheromone that marks the spot and draws more bees to it. Keep moving.

5. Don’t jump into water or hide in brush

This is the movie mistake. University of Arizona Extension warns that the bees may wait for you to come up for air. UF/IFAS says the bees can stay in the area for 30 minutes or longer, so hiding in water or thick brush just keeps you near them.

6. Call 911 for serious incidents

Call if someone has many stings, signs of an allergic reaction, or can’t get away.

If someone else is being attacked

This is the hardest instruction to follow. Don’t run in to rescue them unless you’re wearing a bee suit and have training. UF/IFAS and University of Arizona Extension both advise yelling at the person to run for shelter, calling 911, and staying at a safe distance. Two victims don’t help anyone.

UF/IFAS reports that in Florida, most sting victims are pets and domestic animals, because they can’t escape a tether, pen, or kennel. If an animal is trapped near an active colony, call 911 or local animal control rather than going in yourself. Prevention steps for dogs, horses, and livestock are in Protecting Pets and Livestock from Killer Bees.

After you’re safe: the stingers

Honey bee stingers are barbed and stay in the skin with the venom sac attached. UF/IFAS notes that a stinger keeps pumping venom until it’s removed or empty, so speed matters more than method. Scrape them out with a fingernail, credit card, or dull knife. Wash the area with soap and water, and use ice for swelling.

Get medical care promptly if you’ve been stung many times. University of Arizona Extension sets the threshold at more than 15 stings. Mayo Clinic notes that more than a dozen stings can cause a toxic reaction with nausea, vomiting, diarrhea, fever, and lightheadedness. Children, older adults, and people with heart or breathing problems are at higher risk. Anyone with trouble breathing, a swollen tongue or throat, or widespread hives needs 911. If they carry an epinephrine auto-injector, Mayo says to use it first and then call. Full detail is in How Dangerous Is a Killer Bee Sting?.

Preventing an attack in the first place

Most incidents start when someone accidentally disturbs a nest they didn’t know was there. UF/IFAS notes that a large share of attacks involve people who knew a nest was there and either left it or tried to remove it themselves.

  • Check before you mow, trim, or run power tools. Texas A&M lists equipment vibration (tractors, mowers, trimmers, chainsaws) and loud noises as common triggers. Walk the area first and listen for buzzing.
  • Know the hiding spots. Water meter boxes, irrigation valve boxes, old tires, overturned pots, sheds, and wall voids. USDA’s Tucson lab lists all of these.
  • Keep your distance. USDA recommends staying at least 100 feet from any Africanized colony.
  • Bee-proof your property. UF/IFAS recommends sealing gaps larger than 1/8 inch and screening vents, rain spouts, and utility boxes with 1/8-inch hardware cloth. Inspect weekly during swarm season.
  • Have colonies removed by a professional. Don’t spray, burn, or knock down a colony yourself. University of Arizona Extension warns against shooting, throwing rocks at, burning, or using pesticides on established colonies.
  • Carry epinephrine if prescribed. If you know you’re allergic, keep it on you outdoors.

A note for Ohio readers

Africanized bees are not established in Ohio (see Are There Killer Bees in Ohio?). The same escape plan still works for any stinging-insect nest you disturb by accident. In Northwest Ohio that’s most often a yellowjacket nest in the lawn or a wall. Yellowjackets can sting repeatedly, so get away fast. For removal help near Fostoria, see Northwest Ohio Wasp Removal for wasps and our Bee & Wasp Removal page for honey bees.

Frequently asked questions

Should I stand still if killer bees attack?

No. Standing still works for a single curious bee, not a defending colony. Run to shelter.

Can I jump in a pool or lake to escape?

No. University of Arizona Extension and UF/IFAS both advise against it. The bees can wait above the water.

How far should I run?

Until you’re inside a car or building, or well away from the area. Africanized bees may pursue 400 yards or more.

What if bees follow me into the car?

A few will. Most stay outside. Drive away from the area if it’s safe, then deal with the few bees inside.

Should I pull out stingers with tweezers?

Speed matters most. UF/IFAS says the method doesn’t matter as long as the stinger comes out quickly. Scraping with a card or fingernail is fast and easy.

Related reading

Sources

  • UF/IFAS EDIS ENY-170, “Living with the African Honey Bee”: https://ask.ifas.ufl.edu/publication/IN1205/pdf
  • UF/IFAS Solutions for Your Life, “Africanized Honey Bees”: https://sfyl.ifas.ufl.edu/natural-resources/africanized-honey-bees/
  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee”: https://edis.ifas.ufl.edu/publication/IN790
  • Texas Apiary Inspection Service, “Africanized Bees”: https://txbeeinspection.tamu.edu/public/africanized-bees/
  • University of Arizona Extension, “They are called Africanized Honey Bees”: https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/195020a.pdf
  • USDA ARS Carl Hayden Bee Research Center, “Africanized Honey Bees Overview”: https://www.ars.usda.gov/pacific-west-area/tucson-az/carl-hayden-bee-research-center/docs/africanized-honey-bees/africanized-honey-bees-overview/
  • University of Arizona Extension AZ2011, “Honeybee Basic Biology”: https://www.extension.arizona.edu/publication/honeybee-series-honeybee-basic-biology
  • Mayo Clinic, “Bee sting – Symptoms and causes”: https://www.mayoclinic.org/diseases-conditions/bee-stings/symptoms-causes/syc-20353869
  • Ohio State University Ohioline HYG-2075, “Yellowjackets”: https://ohioline.osu.edu/factsheet/HYG-2075-11

The History of Killer Bees: From Brazil 1957 to Arizona

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The Africanized honey bee didn’t come from nowhere. It came from a deliberate, well-meant attempt to give Brazilian beekeepers a better bee, followed by an accident that let African bees loose. The result became one of the best-documented insect invasions in history. This post walks through the timeline. For what these bees are and how they behave, see What Are Killer Bees? and our Killer Bees 101 hub.

The problem Brazil was trying to solve

No honey bees are native to the Western Hemisphere. USDA ARS notes that Europeans brought honey bees to the Americas starting in the 1600s. Those European bees did well in temperate North America, where their habit of storing big honey reserves for winter paid off. In tropical South America they did poorly.

University of Florida entomologists explain that Brazilian scientist Warwick Kerr traveled to southern Africa to screen African honey bee subspecies for productivity and suitability. African bees had evolved in a tropical climate, and Kerr hoped to breed their strengths into a bee Brazilian beekeepers could manage.

1956: The import

USDA ARS dates the import of African bees to Brazil to 1956. The subspecies was Apis mellifera scutellata, the East African lowland (savannah) honey bee. Kerr’s plan, as UF/IFAS describes it, was to breed gentleness into the African stock through experiments and selection while keeping its good traits.

1957: The escape

The breeding program never finished. In 1957 African bees swarmed out of quarantine. UF/IFAS puts the number at 26 queens that were accidentally released. Ohio State’s entomologists note that the escaped queens mated with local European drones, which produced the hybrid now called the Africanized honey bee.

Several traits made the escape a success for the bee:

  • More drones. Africanized colonies produce more drones, so in a mixed area, European queens are more likely to mate with African drones.
  • Faster development. An African-type queen develops in about 14 days versus 16 for a European queen. The first queen out kills her unhatched rivals.
  • Frequent swarming. Africanized colonies can swarm 10 or more times a year, filling an area with new colonies.
  • Takeovers. Small African swarms can move into European colonies, and the European queen is lost.
  • Pest and disease resistance. UF/IFAS notes that African bees resist many honey bee pests and diseases better than European bees.

1957–1990: Across a continent

With nothing to stop them in the tropics, the bees spread south and north. UF/IFAS estimates the spread through South and Central America at 200 to 300 miles a year, mostly without human help. That earned the bee a reputation as one of the most successful invasive species ever recorded.

The arrival changed beekeeping across Latin America. UF/IFAS’s Solutions for Your Life notes that honey production and pollination dipped during the transition, but countries in South and Central America are exporting honey again, and beekeepers there have adapted their methods. Some South American countries are now among the world’s top honey producers largely because of African-derived bees.

The bees reached northern Mexico several years before the U.S. border, which gave USDA scientists time to study what happens when Africanized bees meet a region already full of European bees. USDA ran monitoring traps and began writing guidance for beekeepers and the public.

The Hollywood years

While the bees moved north, the movies got there first. USDA ARS wrote in 2004 that Hollywood had made Africanized bees “a frightening villain of mythic proportions.” UF/IFAS names two B-movies, Killer Bees (1974) and The Swarm (1978), as how many Americans first heard of them. That’s where the nickname “killer bee” became fixed. The scientific name is still Africanized honey bee, and extension services work hard to replace the fear with facts.

October 15, 1990: Texas

USDA ARS records the date exactly. On October 15, 1990, a swarm was found in an ARS honey bee trap just outside Hidalgo, Texas. It was the first Africanized honey bee colony confirmed in the United States.

Texas tried to slow them by monitoring and regulating commercial bee movement. Natural migration continued anyway. By August 2006, the Texas Apiary Inspection Service had detected Africanized bees in 163 of the state’s 254 counties.

1993: Arizona

University of Arizona Extension says Africanized bees were first seen in Arizona in 1993, reached Yavapai County in central Arizona by 1997, and have since been recorded statewide. Extension now advises that any wild honey bee in Arizona should be considered Africanized. Arizona is probably the state most associated with killer bees today.

By 1996, USDA reported the bees in parts of Texas, Arizona, New Mexico, California, Puerto Rico, and St. Croix. By 2004 the list included Nevada.

Puerto Rico: the bees that got gentler

Africanized bees reached Puerto Rico in 1994. Ohio State’s summary of the research says a 2017 genomic study found a sharp drop in defensive behavior in Puerto Rico’s Africanized bees within about 12 generations (1994–2006). The researchers suggested that conflict with people, island isolation, and low predation may have favored gentler colonies. It’s the only place in the Americas where gentle Africanized bees are known to have evolved. What that means for beekeeping is covered in Can You Keep Africanized Bees?

2001 onward: Florida and the Gulf

UF/IFAS documents Africanized bees near the Port of Tampa in 2001. By 2003 colonies were established around Tampa, and they have since spread through the southern half of Florida. By 2012, UF listed nine states: Texas, California, New Mexico, Arizona, Oklahoma, Louisiana, Arkansas, Alabama, and Florida. Current range details are in Where Do Killer Bees Live?.

Why the march slowed

Early forecasts predicted a fast sweep north, and it didn’t happen. USDA said in 1996 that the spread had been “much slower than predicted,” pointing to interbreeding with resident bees, disease, parasites, and cold weather. Later work tied the limit to climate: roughly 34° north latitude, and possibly heavy year-round rainfall. That’s why there are no established killer bees in places like Ohio. See Are There Killer Bees in Ohio?.

Frequently asked questions

Who created killer bees?

Nobody set out to create them. Brazilian scientist Warwick Kerr imported African honey bees in 1956 to breed a better tropical honey bee. Queens escaped in 1957 and hybridized with local European bees.

How many queens escaped?

UF/IFAS cites 26 queens.

When did killer bees reach the United States?

October 15, 1990, near Hidalgo, Texas, according to USDA ARS.

When did they reach Arizona?

1993, according to University of Arizona Extension.

Why are they called killer bees?

Because of their mass defensive response, made famous by 1970s films. Their venom is no stronger than a European honey bee’s. See How Dangerous Is a Killer Bee Sting?.

Related reading

Sources

  • UF/IFAS EDIS EENY-429, “African Honey Bee, Africanized Honey Bee, Killer Bee”: https://edis.ifas.ufl.edu/publication/IN790
  • UF/IFAS EDIS ENY-147, “Differences Between European and African Honey Bees”: https://ask.ifas.ufl.edu/publication/IN784
  • UF/IFAS EDIS ENY-170, “Living with the African Honey Bee”: https://ask.ifas.ufl.edu/publication/IN1205/pdf
  • UF/IFAS Solutions for Your Life, “Africanized Honey Bees”: https://sfyl.ifas.ufl.edu/natural-resources/africanized-honey-bees/
  • USDA ARS, “Africanized Honey Bees: The March North Has Slowed” (1996): https://agresearchmag.ars.usda.gov/1996/mar/forum/
  • USDA ARS, “The Latest Research on Africanized Honey Bees” (2004): https://www.ars.usda.gov/news-events/news/research-news/2004/the-latest-research-on-africanized-honey-bees/
  • Texas Apiary Inspection Service, “Africanized Bees”: https://txbeeinspection.tamu.edu/public/africanized-bees/
  • University of Arizona Extension, “Feral Honeybees” (2023): https://extension.arizona.edu/sites/extension.arizona.edu/files/attachment/FeralHoneybees.pdf
  • Ohio State University BYGL, “Myths and facts – Africanized honey bees”: https://bygl.osu.edu/node/2431

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