Suzanne and I arrived home on a hot afternoon finishing a long drive this past summer. After carrying in the heavy loads from the car to the house, I walked the hive rows of my main research apiary by the bee house. We had only been away for one night. For me though with bees, that absence can be close to eternity, even during a drought. The cornfield across the road that was tall and green from earlier in the season had slowly been turning mostly dry and brown.
With a mix of frame hives, top-bar hives and long hives, some 25 hives in all, I thought, They’re whiny. When potential robber bees flit around hive entrances, their buzz sounds a little higher. In still air, when robber bees test the defenses of numerous hives in a quiet rural apiary, the place takes on a noticeable whine of fast-flying unloaded bees. The sound differs from the lower hum of bees foraging in a nectar flow or for water. (Listen to your hives before opening them.)
At this point, I was wondering, which hive did the bees find to rob? I found none. Except. A small cloud of bees circled one of the nucs (see Figure 1). From a distance, seeing the flying bees backlit by sunlight, their slow searching circles suggested confusion, not aggressive honey removals.
At the hive entrance, the scent-fanning bees reinforced my initial impression of confused bees, definitely not robbing (see Figure 2). Moreover, this colony was a small one. Now bees stood crowded around the entrance, some scent-fanning. Where did they come from? I needed to open the nuc without a lit smoker (absolutely not recommended, but needed here). I had to see the bees on the combs with the least disturbance to them.
My entry into the top-bar nuc was from the end opposite the entrance side of the hive by removing the plywood (see Figure 3). Seeing the bees on the combs from the rear, I could tell the bee population had more than doubled (see Figure 4). At this point a reasonable explanation is colony usurpation.
Colony usurpation is when a swarm, which could be fairly small, enters an established colony, called the host colony, kills its queen, called the resident or host queen, and replaces her with their usurpation queen. (This behavior is called social parasitism.) I see these swarms in the summer when little or no nectar is coming in, or during a summer cotton nectar flow, which is not an intense nectar flow, at least in southeastern Virginia at the northern extent of cotton production.
So far from what I have observed previously, initially two queen balls form when the swarm first rushes into the hive. One ball forms around the usurpation queen, usually near the hive entrance. Another ball occurs deeper in the brood nest. It contains the resident queen. The takeover process can occur quickly. My quickest time estimate of a usurpation that occurred in an observation hive in my bee house was about 13 hours. Therefore, the colony had accepted the usurpation queen, that is, released her from the ball. The bees continued balling the resident (mother) queen until she died, about three days from the initial invasion.
Understand the ramifications of what I watched in my observation hive. The usurpation queen began laying her genetic eggs in the brood nest of the resident queen (her resident workers would rear the usurpation brood), while only inches away, down on the hive floor, the resident mother was slowly dying in a ball. We will see more compelling results of the takeover.
If a beekeeper finds a usurpation swarm at this time, which persists for a longer duration, only one queen ball is present (the one with the resident queen). Trying to diagnose a very recent usurpation event usually calls for searching for queen balls. In my searching, I proceed all the way down to the bottom board because the ball of bees frequently falls slowly down there, unless it encounters an obstruction.
With that in mind, search anywhere a queen ball could become caught in burr comb or tight gaps between the end bars and the hive walls. A queen ball search is more time-consuming because the ball of bees blends in with small clusters of bees. Before searching, try looking through the entrance slot with a bright (LED) flashlight. A knot of bees that seems to persist against small amounts of smoke could be a ball.
From fighting between the usurpation swarm and colony’s bees, the dead accumulate in front of the hive. In the worst cases, I have seen mortality numbers resemble a light to moderate pesticide kill. Besides confusion with a pesticide kill, this symptom is unreliable when showing low mortality after night-foraging wildlife and insects remove some of the dead bees. Skunks for example are well known for this removal, leaving small balls of chewed-up exoskeletons. Much less appreciated are night-foraging ants. In our area, the larger ants can quickly drag away dead bees. I know from a strong nearby nest that they can clear 300-500 dead bees scattered over the ground in front of a usurped colony.
For the usurpation of this nuc colony, the small number of scent-fanning bees and increase of bees in the nuc made it appear the swarm had just finished entering the hive. I expected two queen balls: one near the hive entrance containing the usurpation queen, and one deeper in the brood nest containing the resident queen. It is reasonable to figure the usurpation queen becomes immobilized in a ball upon entering the hive, for protection from the hive bees. The resident queen becomes balled farther from the entrance, wherever she happens to be when the usurpation begins. If the swarm had just entered the hive, not enough time had elapsed for dead bees to accumulate under the entrance of the nuc.
Initially I found one small queen ball on the comb, close to the entrance, as expected. After a couple of slow detailed searches, I could not find another queen ball. For three combs of bees, covering them mostly in a single layer, searching was easy. I just could not find another queen ball or queen in the nuc, although eggs were present in the brood nest.
I decided to remove the usurpation queen from the ball to make sure I had control over at least one queen (see Figures 5 and 6). I carefully detached the ball from the comb and slowly plucked the bees from the ball to the last bee –– and guess what! No queen! The bees balled a worker deep in the ball.
Since all the bees resembled each other, distinguishing hive bees from usurpation bees was not possible. A couple of explanations are possible. Resident bees could have been balling a worker that had the odor of a foreign queen, here the usurpation queen. During more typical conditions, I have seen queens enter the wrong nuc after a mating flight and be immediately captured in an aggressive ball and killed, unless I quickly removed her. It might also be usurpation bees forming a ball around a worker who happened to have the odor of their queen. Here the ball would be more for protecting the queen. (Sometimes with protection balls, the bees form a loose ball around their mated queen. She is easy to remove from the ball. With an aggressive ball containing a mated queen, I must carefully remove the bees, particularly the last ones in direct contact with the queen. Mated queens have some inherent partial protection from being stung. Unmated queens seem to have less of it.)
Another odd characteristic of this usurpation was the low frequency in fighting between the established colony (the nuc) and the usurpation swarm bees in the hive. A few bees squabbled, locked together, and spun around on the hive floor, trying to sting each other.
The reduced fighting was consistent with the next big observational reveal. Even with the large increase of the bees in the hive, not all of the usurpation swarm was in the nuc. The usurpation swarm was on the ground in front of the nuc (see Figure 7). I have seen usurpation swarms come to this side of the bee house and take over a colony, even strong queenright ones, passing by weaker colonies, even queenless ones.
Sometimes the defending colony bees manage to sting the usurpation queen. I have been at the hive entrance when it occurred a couple of times, so far always during the initial rush of the usurpation swarm storming into the hive. In those initial (unseen) moments, I imagine the usurpation queen could be among the hostile colony bees and maybe not enough protective swarm bees are around her. Once from a frame hive, I saw the usurpation queen crawl out of the entrance. She had a leg or two (her hind legs if I remember correctly) dragging, paralyzed, a sure sign of being stung. The usurpation queen carries all the genes of the colony, hers and from her multiple drone mates. If the usurpation queen dies, the takeover fails (assuming the usurpation worker bees do not display any unusual reproductive behavior, which so far seems to be the situation here in Virginia).
Even if all of the usurpation workers perish in the fighting, leaving their queen as virtually the sole survivor, the takeover is successful. As mentioned above, the usurpation queen will lay her eggs in the brood nest. The hive (host) nurse bees will care for the brood. Eventually usurpation progeny will replace the workers of the former queen. The usurpation bees will survive the winter on honey made by the host bees. In addition, the usurpation bees will live on combs built by host bees, bees unrelated to them (as far as we know). A seemingly destitute summer swarm, hiveless without combs or winter honey, can now take them instead of make them (breaking the old rules of honey bee ecology in a temperate environment, built on rapidly accumulating provisions before winter arrives).
When the usurpation queen enters the hive, her bees should quickly form a protective ball around her. (That hypothesis needs verification to confirm the bee origin.) The swarm on the ground balled its queen while the bees scent-fanned nearby at the nuc’s entrance. It seemed the swarm almost had a successful entry for this nuc.
Except somehow in this current case, the bees balled their queen too soon, not waiting until she entered the nuc. What conditions stimulate that particular balling response remains unclear. Some interaction between the host bees and foreign bees (outside of the host hive) in conjunction with the volatile pheromone components from the usurpation queen would be…