P&PDL Picture of the Week for
June 13, 2011

Oh, the Things We Can Learn From a Swarm of Honey Bees

Tim Gibb, Insect Diagnostician, Purdue University

Large swarms of honey bees that suddenly appear on homes, bushes or in yards sometimes send people into shock.  This is because a swarm may contain several hundred to several thousand bees that people have come to fear as dangerous stinging insects.  Swarming bees are actually very non- threatening and the swarming behavior is a very interesting phenomenon and a natural means of reproducing honey bee colonies. 

Swarms usually occur in late spring or early summer when a queen bee leaves the original colony due to overcrowding and takes with her a large group of worker bees to find a new home.  These bees all fly off as a group but then may cluster on a tree limb, shrub or other object for an hour to a few days, while scouting bees are searching for a new nest site.  When a suitable location for the new colony, such as a hollow tree, is found the cluster breaks up and flies to it.

People need not be overly frightened by bee swarms because the bees at this stage of their life cycle lack a hive to defend.  Until they have a new hive, they are not very aggressive. This does not mean that bees will not sting if they are provoked, however. They simply have no hive to defend and thus are much less likely to attack.

In most situations, witnessing a swarm of honey bees offers a rare learning opportunity.  Swarms are beautiful in their own right and should be appreciated (from a safe distance).  They are a marvel of nature and offer an opportunity to teach people, young and old, about how bees communicate, their biology (possibly an opportunity to discuss the birds and the bees) as well as an opportunity to appreciate their value to the environment and the tremendous benefits that they provide people.  Pollination is probably the most valuable of these benefits, followed by honey and wax production. 

So, in most situations when a honey bee swarm is found on a tree, shrub or house, no action is required. Remember that swarms are almost always temporary and the bees will move on within hours, or at most a few days, if you patiently ignore them.

Having said that, there are a very few times and places where honey bees can create an annoyance or a nuisance, and for sting-sensitive individuals, a possible health threat.

Only if a serious health threat is present because of the location of the swarm, such as in a highly traveled public area, should you need to do anything with a bee swarm. An experienced beekeeper may be paid to come and gather the swarm and relocate it for you. Note that most beekeepers do not want the bees in their own hives because wild bees often have diseases and parasites that can be introduced into their own colonies.

If beekeepers cannot be found, you may call a pest management professional to kill the bees or you may choose to do it yourself by spraying the swarm with soapy water (up to 1 cup of liquid dishwashing detergent in a gallon of water) or synthetic insecticide. Soapy water sprays are preferred because the bees are less agitated; aerosol wasp and hornet sprays are more likely to irritate the bees before they die, increasing the chances of someone being stung.  In either case, spraying a honey bee swarm is a risky operation because of the large number of bees present. Waiting until after dark, when bees are less active, will help reduce chances of a sting.

If honey bees nest in an attic or in the walls of a home, they should be removed or killed promptly. After several months, honey bees may have stored a considerable amount of honey, food reserves and brood.  Should the bees die at this time, the wax and honey will melt and run and the decaying brood and honey and comb will attract undesirable rodents and insects. In these cases, you may have to seek the assistance of an exterminator to work closely with a experienced carpenter to kill the bees, open the wall and remove the hive and then restore the structure.

You can prevent bees and other insects from nesting in walls by preventive maintenance. Honey bees will not create an entrance to a nest.  Rather, they look for an existing entrance, so periodic inspection and sealing openings and cracks where bees can get in, is all that is necessary to prevent them from occupying spaces in walls.

Honey bees have recently had difficulty surviving in the wild.  They are becoming less common throughout the U.S. and even seeing a swarm of bees is a rarity as of the last few years.  Because of the value that these insects are to our environment, any that live away from our homes and out of reach of sensitive people, should be encouraged and protected.


Click image to enlarge

Honey bee swarm

Honey bee swarm on branch

Closeup honey bee swarm

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service