Although bees are not as aggressive or dangerous as their larger wasp cousins, an infestation of bees is far more than just a nuisance. Bees can form massive colonies of as many as 50,000 individuals and deliver painful stings in sustained swarming attacks. They also can cause extensive damage by forming honey-bearing nests inside walls and other hollow structural cavities. When a person discovers a colony of aggressive stinging insects, the first reaction often is panic. But if you know how to spot an infestation, what to do and what not to do, you can handle your bee problem safely.

Know What You’re Dealing With

There are more than 20,000 bee species, and it’s easy to confuse many of them with wasps. Although bees and wasps are related, it’s important not to mix them up because wasp infestations must be dealt with differently from bee infestations.

Among the easiest identifiers are hair—wasps have smooth bodies and bees are fuzzy. Bees have straighter bodies than wasps, which are known for their tiny waists.

Among the bees most commonly found in the US are carpenter bees, which are solitary, and bumble bees, which are large, slow and easily identifiable by their black-and-yellow-striped bodies.

But if you’re having an issue with bees in the US, chances are you’re dealing with the familiar domestic honeybee, which is common all over the country. About one-half-inch long and oval shaped, honeybees are golden yellow with brown stripes.

Think You’ve Got an Infestation? Know the Signs

Unwelcome bees can make their homes in a variety of ways and places, both inside the house and out.

Some bees, such as bumble bees and miner bees, burrow in the ground. Carpenter bees bore small tunnels in wood. Common honeybees create hives in existing empty chambers, such as hollows in trees, spaces in walls and other natural or structural voids. Other common trouble spots are under eaves and in attics, garages and sheds.

An unidentified but persistent buzzing or humming sound could signal the presence of an active colony behind walls or in other hiding places, as could dark spots on walls or ceilings. The most obvious indicator, however, is the presence of an unusually large number of bees outside the house, particularly if they’re flying into or out of gaps and holes in your home or an outlying structure.

Tip: If you notice an unusually large number of bees in your yard, watch them from a safe distance and note where their return flights end. That likely is the entrance to their hive.

Know the Difference Between an Infestation and a Temporary Cluster

Massive, scary-looking clusters of bees sometimes appear all at once on the sides of homes, trees or streetlights. Although startling, this phenomenon usually is neither dangerous nor permanent, and no action is required—other than keeping your distance. The sudden arrival of an entire colony is not an infestation. When traveling bee swarms sense danger, they stop temporarily to huddle around their queen. Bees are docile in this mode and usually will move on within 24 hours. If the cluster is a safe distance away, wait a day. If the bees don’t leave within 24 hours, call a beekeeper (see below) to collect them. Never try to scatter them by spraying them with water or swatting at them. Bees may interpret these actions as a threat to the queen, which could trigger an attack.

Call a Beekeeper, Not an Exterminator

Bees, which play a crucial role as pollinators, have suffered a massive population decline in recent years, and they shouldn’t be harmed unless it is absolutely necessary. Since the year 2000, the rusty patched bumble bee has been reported in just 13 midwestern, eastern and southern states and one Canadian province, down from 28 states, the District of Columbia and two Canadian provinces in the late 1990s. In 2017, it became the first bee listed on the federal endangered-species list, which makes it illegal to destroy its hives—but bees, in general, have become a dwindling and precious resource.

Even if you are less than sympathetic to their plight, which is natural if they are invading your home, all credible members of the pest industry are aware of and sensitive to the dwindling number of bees. Willingness to eradicate a bee colony is a red flag that you might be dealing with an unscrupulous or inexperienced contractor.

Beekeepers, on the other hand, will safely collect bees alive, remove their hive from your home or yard and relocate them to a man-made hive. Visit the American Beekeeping Federation website to find a registered beekeeper in your area.

Understanding Bee Aggression

When honeybees sting, they make the ultimate sacrifice. A honeybee can’t remove its barbed stinger once it is lodged in human skin, so when the bee pulls away, the stinger—and a sizable chunk of the bee’s body—remains behind. The bee dies from its injuries, but it leaves behind a potent chemical marker that serves as a beacon for its surviving comrades. No matter where you run, the stinger embedded in your skin leaves a chemical trail that the agitated bees will pursue.

How to Handle an Attack

If you’re stung by a bee outside, don’t pause to remove the stinger or tend to the wound. Instead, quickly leave the area, preferably retreating indoors or into a vehicle, as other bees could be preparing for a follow-up attack. Walk briskly but don’t run or flail your arms, since sudden movements can further agitate bees that already are in a heightened state of alertness.

If you’re subjected to a swarming attack, however, run as fast as you can while yelling for any companions to do the same. Don’t stop to help others unless it’s to assist a child, disabled person, elderly person or someone who is allergic to bee stings. If some bees follow you inside, turn on the lights, which will confuse the bees and send them flying toward the windows. If no car or building is close by, continue running away from the sun to avoid casting a shadow or duck behind a tree and use it as a shield until the bees stop their attack. European honeybees will stop pursuit after 30 to 35 feet. Africanized honeybees, on the other hand, will chase and attack for 10 times that distance.

If shelter is not available, you’re going to sustain some stings. Pull your shirt over your head to protect your eyes, mouth and throat, but don’t slow down. Never jump into a pool or other water. Bees often wait for victims to surface and then continue the attack, leaving the victim nowhere to retreat. This can lead to severe facial stings and even drowning.

If you know that you are allergic to bee stings, carry an epinephrine injection pen at all times.

Beware of Africanized “Killer” Bees

Domestic honeybees, which are comparatively docile, are European by ancestry. Africanized honeybees, often called killer bees, look the same but are much more aggressive, dangerous and persistent in their attacks. They send guards to attack perceived threats in significantly larger numbers from a much greater distance and remain in an agitated state for much longer periods than do European honeybees. If you think you’ve spotted a colony of killer bees (see below), get indoors and call 911.

Tips for spotting killer bees:

Killer bees were first identified in the US in the Southwest and still are most prevalent in that region, with millions of colonies ranging from Texas to the West Coast. Their range is expanding, and they now can be found in Southern Florida and, most recently, in parts of the Southeast and Appalachia.

Unlike European honeybees, Africanized bees will nest in underground cavities or exposed locations such as on tree branches. They colonize in smaller groups and often nest in smaller, man-made voids such as water meter boxes, which are too small for European colonies.