Beekeepers are often admonished to keep a close eye out for signs of swarming. That’s good advice. But other than frames covered with forests of queen cells, what do swarm preparations look like?
Most of the time there are signs of what's to come, if you know where to look for them.
In the spring, a hive that is boiling over with bees is always a prime candidate for swarming. If you can, add more drawn comb immediately to both the brood nest and the supers. Bare foundation rarely has any effect at dampening down a hive’s interest in swarming since until it has been drawn out, it doesn’t offer the bees more space for either brood or nectar storage.
A hive that’s making a lot of drone cells may also be ripe for swarming. These can be on the margins of worker frames, or annoyingly stuck on the tops of frames between boxes. Those are frequently torn apart when doing inspections. (Don’t waste this opportunity to examine the exposed pupae for varroa mites.) If none of the hives in your yard are raising drones, it’s probably still a little early for swarming.
Another sign that the bees may be planning to leave soon is when they begin to backfill emerged brood cells with nectar. This can also happen simply due to not having enough room to store a sudden flush of incoming nectar. Beekeepers should make sure there is still available room in drawn comb in their supers and offer more if needed. Cells backfilled with nectar look very different from cells of young larvae swimming in a pool of brood food.
Larvae floating in their little drops of moisture are at the very back of cells. This is always considered a good sign that the colony has ample nutritional resources and plenty of healthy nurse bees to make the brood food. Because the larvae at this stage are still very tiny, the quantity needed to surround them is also very small - just a thin wash.
In contrast, cells being back-filled with nectar are often half or three-quarters full, with a distinctly concave look to the surface. Because a swarm leaves with a good share of the hive’s honey stores in their crops, during the countdown to departure, a colony may act like panicked hoarders filing any available space with nectar to tide over the remaining bees until the foraging population has rebounded.
Bees normally make queen cups on frames all season long. In the spring though, the pace of queen cup making picks up. And a wise beekeeper looks in each one to see if there’s an egg or a tiny drop of royal jelly. If you see that, they are no longer queen cups; they are full-fledged queen cells. Removing them will only buy you a few days’ grace to make other plans, if even that much. Sometimes the quickest way to see down into the bottom of a queen cup is to use your hive tool to make a little slit in the side. A flashlight is also useful to catch the glint of royal jelly.
And finally, when you see your queen, if she’s looking surprisingly svelte, that isn’t something to compliment her on. She has been slimming, but that’s involuntary. Her attendants have put her on a diet and been hustling her about, in order to reduce her egg laying, and to get her back into flying trim so that she can endure the swarm flights.
If you see any of these signs, then you can assume that whatever steps you have already taken to discourage the natural urge to swarm are unlikely to be successful. And if you want to keep your bees, you’ll need to act quickly and do some type of split to keep them in your boxes. By all means, add more drawn comb to the brood nest and the supers if you can. But by this stage, even adding space may not be enough to save the day.