The Chicago River has made great strides towards becoming a clean and vibrant waterway. Reports of aquatic wildlife, including muskrats, turtles, beavers, and even otters have become common place. While walking to lunch, I’ve seen a blue heron perched on a grass covered outcropping of concrete. I’ve noticed the increased recreational activity as kayakers pass below my office building windows nearly every day. But to see a natural phenomenon in the heart of the Loop – one so rare that in a lifetime of camping, hiking, and backpacking I had yet to witness – had never crossed my mind as a possibility.

Yesterday during lunch, crossing the Jackson Street Bridge, I spotted a cloud of flying insects sparkling in the bright sunlight ahead. My first thought was that it must be a cloud of gnats and I prepared to spit out the stray that would inevitable fly directly into my mouth. But as I passed through the cloud one landed on my hand, and I was surprised to gaze upon a honey bee. Yes, flying all around me on a busy Chicago sidewalk was a swarm of honey bees! I quickly exited the swarm and waited a moment before gently brushing the bee off my hand.

Some passersby were intrigued, took photos, and chattered about how bizarre it seemed. Others briefly panicked and flailed their arms around their heads (really?). It took a second pass for me to notice that the bees flying around were not the entirety of the swarm, rather they were a tiny fraction, the outliers, the business as usual traffic of bees scouting or preparing to land. A much larger cluster of bees was gathered on the bridge house, out of reach but still well within sight, at least to those who cared to stop and look for a moment.

Why would all these bees be swarming the streets of Chicago? Well, it turns out that honey bees are even more interesting than I’ve always thought. Not only does the individual bee go through its own life cycle, but the colony itself reproduces into two and some times more colonies through the process of swarming. In this regard, the colony is considered a superorganism by entomologists.

Throughout the course of the spring and summer the queen bee is busy producing additional workers and, later, drones. The workers are busy foraging, guarding, tending the brood, and regulating the hive’s temperature. They also feed one another and, in a process known as trophallaxis, communicate by passing on pheromones left behind on the food. The queen produces her own pheromone and, in doing so, attracts and instructs the workers. As the colony expands, crowding reaches a critical threshold where a great number of bees are no longer receiving the queen’s pheromone. To them she no longer exists and they go about the business of producing a new queen (those traitors!).

Before the new queen is born, the old queen must leave. What anarchy would entail if one hive had multiple queens? I’ll leave it to Pixar or DreamWorks to imagine the consequences of such an outrageous breakdown in order! The old queen takes perhaps 60% of the workers, the prime swarm, with her in search of a suitable place to form a new hive. Not such a bad settlement in the overall scheme of things.

But the queen is not the strongest flyer in the world, often she must stop to rest. The worker bees will form a clump, gathering around the queen to protect her. Meanwhile the queen will send out scout bees to continue searching for a suitable site. This particular swarm has calmed down since I first encountered it. Pedestrian traffic is now blissfully unaware that it is even there, perched just above their heads as they walk by. It is uncommon for a swarm to cluster for more than three days, as its food supply is very limited during this stage. They are approaching the three day mark according to word on the street (literally, I overheard a guy on the street say they were there two days ago). I expect they will have moved on to their new home by tomorrow. I hope they will, in fact, because swarming is a vulnerable time in the life of the colony. Good luck to you, Jackson Street honey bees.

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Scott Mohan

Latest posts by Scott Mohan (see all)

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