April Showers Bring May Flowers . and Swarms

By Diane Wells

A honeybee swarm.
Photo by Diane Wells.

As tempting as it may be to believe so, the sole purpose of a honeybee swarm is not to irritate the beekeeper or the beekeeper's neighbors. No, a swarm is simply a mechanism for colony reproduction. That's it. Unlike the individualized form of reproduction that takes place within the colony, when the queen lays fertilized eggs day after day, colony reproduction is the species' push to persist. By dividing one colony into two, it increases its chances of surviving and passing on its genetic material. Two small colonies in two different locations are more likely to survive a catastrophic event, such as a marauding bear, lightning strike to the nest tree or a nectar dearth, than one large colony. If they did not swarm, honeybees would not have the means to expand their regional population. So, as bothersome as it may be for beekeepers, a swarm is worth admiring, but for a second, because it signifies life and the drive to carry on.

The swarming instinct is not fully understood. We do know that it typically kicks into gear when bees start to feel crowded. A lack of empty cells for the queen to lay eggs in and idle workers give this sense. Also, the queen releases a chemical pheromone, long referred to as queen substance, that is picked up by her attendants and passed on from one worker to the next. If that pheromone becomes faint due to overcrowding or because she is getting on in age, the workers will feel compelled to rear another queen. More often than not, crowding occurs in the spring, when the queen is laying eggs at her maximum egg-laying rate (up to 2,000 a day), in anticipation of summer nectar flows. A robust and booming colony, lengthening days and rising nectar flows feed the desire to swarm. An unusually mild winter, a severe winter that causes significant winterkill and a cool, rainy spring will fuel the instinct as well.

Preparations for swarming begin many weeks prior to the act itself. Worker bees will start to form queen cups, waxy precursors to queen cells, the cells used to rear queens. Scout bees will commence the search for new nest cavities. A little more than a week before swarming, the queen will lay eggs in the queen cups. The workers will then lengthen the cups, turn them into queen cells and begin tending eggs and plying larvae with royal jelly. The queen will start to lose weight in anticipation of flying. Workers will gain weight in anticipation of going without food in the course of the move.

Depending on your latitude, a swarm can emerge anywhere from mid-May through July. Here in northern Vermont, swarms typically emerge in late June or the first week of July. For those further south, emergence tends to occur earlier. Swarming can and does occur in early fall, but it is much less frequent, with only 20 percent of the swarms in a given year occurring in late August and September.

A swarm consists of 30 to 70 percent of the colony's worker bees, a handful of drones and their queen. Those taking part will leave the hive within minutes, fly in what appears to be a chaotic cloud for another minute, then quickly coalesce. In no time, what was thousands of individuals seemingly becomes one organism. This unique unit of life will initially cluster on some sort of structure, be it a tree limb, scarecrow or birdbath, within 100 yards of its original hive and remain there for up to 48 hours. Contrary to common thought, a swarm is not cross and will not defend itself against two-legged onlookers. Because the bees do not have brood or a food supply, they have nothing to defend. Once a viable site is agreed upon, the swarm will leave the cluster site and fly to the newfangled nest cavity that can be up to several miles away.

A skilled beekeeper can manipulate a hive in such a way as to prevent or control the swarming instinct, perhaps not 100 percent of the time, but the vast majority of the time. Because colony division translates into a significant reduction in honey production and pollination services, it is in the beekeepers utmost interest to prevent the colony from dividing itself. That said, swarms happen. And with the recent surge of interest in beekeeping and the rising number of novice beekeepers, I would bet my honey extractor that honeybee swarms are increasingly common.

If you are not a beekeeper but find yourself the proud new owner of a swarm, chances are a local beekeeper will come to your rescue. Depending on its size, a swarm can be equivalent to a 3-pound package of bees (the most common unit by which honeybees are purchased) and signify a new colony for the beekeeper that wishes to collect it. A new colony, that is, if the swarm did not originate from his or her apiary. The swarm's value holds true, though, and it is worth containing and either returning to the original colony, combining it with another weak colony or starting one anew.

If you spy a swarm dangling from a tree branch or discover a newly established colony in your barn, attic or even barbecue grill (yes, it has happened), contact the local chapter of your state's beekeeping association as soon as you can. How? The best way to go about it is to look them up on the Internet. You'll soon find your association has a Web page that lists beekeepers who are local to you and willing to capture a swarm or remove an unwanted colony. The Maine Beekeepers Association ( has even formed a swarm team that you can contact via email, phone or by filling out a form on their website. The resources are there for you to use, so by all means, use them.

The author, a regular contributor to Farming, is a biologist who lives and farms in Vermont's Northeast Kingdom