Why Do Bees Swarm?

Bees usually swarm in the spring, but occasionally do so in summer or even in fall. Why do bees suddenly decide to get up and move en masse? It's actually normal bee behavior.

Bees Swarm When the Colony Gets too Large

Honey bees are social insects (eusocial, technically), and the honey bee colony functions much like a living organism. Just as individual bees reproduce, the colony must reproduce, too. Swarming is the reproduction of a honey bee colony, and it occurs when an existing colony subdivides into two colonies. Swarming is essential to the bees' survival. If the hive becomes overcrowded, resources will be scarce and the colony's health will begin to decline. So every now and then, a bunch of bees will fly out and find a new place to live.

What Happens During a Swarm

When the colony gets too crowded, the workers will start making preparations to swarm. Worker bees tending to the current queen will feed her less, so she loses some body weight and is able to fly. Workers will also start raising a new queen by feeding a chosen larva large quantities of royal jelly. When the young queen is ready, the swarm begins.

At least half of the colony's bees will quickly leave the hive, prodding the old queen to fly with them. The queen will land on a structure and workers will immediately surround her, keeping her safe and cool. While most bees tend to their queen, a few scout bees will begin searching for a new place to live. Scouting may only take an hour or so, or it can take days if a suitable location proves difficult to find. In the meantime, the large cluster of bees resting on someone's mailbox or in a tree may attract quite a bit of attention, especially if the bees have alighted in a busy area.

Once the scout bees have chosen a new home for the colony, the bees will guide their old queen to the location and get her settled. Workers will start building honeycomb and resume their duties raising brood and gathering and storing food. If the swarm occurs in spring, there should be ample time to build the colony's numbers and food stores before the cold weather arrives. Late seasons swarms don't bode well for the colony's survival, as pollen and nectar may be in short supply before they've made enough honey to last the long winter months.

Meanwhile, back in the original hive, the workers that stayed behind tend to their new queen. They continue to gather pollen and nectar and to raise new young to rebuild the colony's numbers before winter.

Are Bee Swarms Dangerous?

No, actually quite the opposite is true! Bees that are swarming have left their hive, and don't have brood to protect or food stores to defend. Swarming bees tend to be docile, and can be observed safely. Of course, if you are allergic to bee venom, you should steer clear of any bees, swarming or otherwise.

It's fairly easy for an experienced beekeeper to collect a swarm and move it to a more appropriate location. It's important to collect the swarm before the bees choose a new home and start producing honeycomb. Once they find a place to live and go to work making honeycomb, they will defend their colony and moving them will be a bigger challenge.

Sources

• Honey Bee Swarms, University of Arkansas Cooperative Extension Service website.
• Honey Bee Swarms and Their Control, Texas A&M Agrilife Extension website.
• Swarms, University of California Davis website.
• Swarm Control for Managed Beehives, University of Florida IFAS Extension website.