Tom Turpin
Professor of
Purdue University







When the Bees Swarm

There is a Midwestern ditty that goes:

            A swarm of bees in May is worth a load of hay,
            A swarm of bees in June is worth a silver spoon,
            A swarm of bees in July, just let them go by!

The swarm referenced in the ditty is of honey bees. The advice offered is whether or not the swarm is of value and should be captured. It also tells us something about the time of the year when honey bee swarms were seen.

Swarming is the process used by some social insects to establish new colonies. The social insects that produce swarms are those that have colonies that exist for more than one year, including ants, termites and honey bees. Colonies of these insects are called perennial, just as are plants that live from year to year.

In the ants and termites, large numbers of winged males and females emerge from established nests, find a mate, and settle down to establish a new colony. The process is more complicated in honey bees. In their case, a newly emerged queen goes on a mating flight, but she returns to the home colony. No colony of honey bees, or any other organization for that matter, can have two rulers, so the old queen and a sizable number of the mature bees leave. Such a group of temporarily homeless honey bees is known as a swarm.

It is during this homeless wandering state of the bees that beekeepers can capture the swarm and use it to establish a new colony. Seeing a honey bee swarm is exciting for most people, and such an observation is one of the rites of late spring and early summer in the Midwest. But encounters with a swarm of bees, once commonplace, is getting rare.

Where have the swarms gone? Generally the answer is related to the lack of wild colonies of honey bees. Wild colonies of bees once were common in holes in trees, giving rise to the term "bee tree," in walls of barns or houses, and even in piles of rocks. Many swarms originated in these unmanaged colonies. For the most part, serious beekeepers try to keep their colonies from swarming since the reduced number of bees weakens the hive and reduces honey production.

So where have the wild honey bee colonies gone? They have died, mostly as a result of infestations of mites. Yes, mites. There are two species of mites that live on and cause problems for honey bees in the Midwest. One is the Varroa mite, which attaches itself to the adult bees and feeds on immature bees in the comb. The other mite is called the tracheal mite because it lives in the breathing tubes of the bees. Together, these mites have killed many colonies of bees or contributed to colony death during the winter. The result has been very few colonies of wild bees and few swarms in May, June and July to catch or just let go by!


Writer: Tom Turpin
Editor: Andrea McCann