How many beekeeping books can you recall listing the ways honey bees replace their queen bees? Here is the list: swarming, supersedure, and emergency queen loss. This list needs to be updated now, because for probably about 10-15 years, maybe longer, the bees have had a fourth way to replace a queen (here in the mid-Atlantic).
The additional way is by colony usurpation where a swarm, usually fairly small, enters a colony, called the host colony, kills its queen, called the resident queen, and replaces her with their usurpation queen. (This behavior is called social parasitism.) I see these swarms during a summer dearth, or in the summer when nectar is scarce or during a summer cotton nectar flow (not an intense nectar flow, at least here in southeastern Virginia, which is at the northern extent of cotton production).
This takeover process can occur quickly. My quickest time estimate, using a usurpation that occurred in an observation hive in my bee house, was about 13 hours. Moreover in the host colony, this kind of queen replacement has no queen cells and leaves no remnants of them found with the other three types of recent queen replacement.
While the lack of queen cells may seem obvious, beekeepers have reported to me their marked queens vanishing and replaced by unmarked ones within a few days or a week. In the hive, or nuc, they could not find any structures suggesting a recent queen cell. Those situations are quite perplexing, verging on impossible, if one’s thinking consists of only the three traditional ways of queen replacement. Include usurpation, and those situations become quite feasible. To me it shows why beekeepers should stay current with all the fundamental behaviors displayed by their bees.
Most every summer I see some evidence of at least one, usually more, usurpation event in my apiaries. For most usurpation encounters, I am fairly sure it occurred, although not much remained that was distinctive enough to photograph or record. Sometimes I find this evidence when just patrolling my apiaries in the summer, looking for typical seasonal problems: mass robbing, chronic robbing, signs of too many small hive beetles, entrances showing fewer bees causing suspicion of a population reduction, or any harassment by hornets (usually the large Vespa crabro, which can forage at night, and become disoriented and attracted to bright nearby lights).
On these brief visitations, I usually do not open any hives unless I see symptoms that warrant it. Rather I walk the hive rows (entrance side) seeing what the bees have been discarding. I have a small extra-bright LED flashlight, and I examine the entrance slots to check for population reductions, or for what could be falling from a cluster but not discarded (sometimes dead pupae from weak colonies). (I always keep about three of these small flashlights on the bee truck for inspecting a queen’s young and old larval patterns, which tells me more about a queen than her sealed brood pattern.) I also listen for and search in and around the apiary for small swarms, but they can be exceedingly difficult to find unless they have landed out in the open.
On a patrol to one of my frame-hive apiaries, even before getting out of the bee truck, I could see suspicious bee flight at the other end of the apiary (see Figure 1). Looking down the row of hives, too many bees were approaching from due south and not from the east, across the large field, the normal flight direction of the foraging bees. A small swarm was entering the apiary.
Let’s pause here. In your prior beekeeping knowledge, how could you explain, if asked, why in the summer would a small swarm be coming into an apiary? Not leaving the apiary, but rather, I have had these swarms come out of the woods into my rural apiaries with no place to shelter a swarm trying to start a new brood nest. Why would a swarm do that? In the “former bee-behavior rules for a temperate climate” a small swarm would be an absconding swarm that abandoned its nest site, and would be destined to perish in isolation. Therefore, a summer swarm coming into my apiary is already a suspicious warning of potential usurpation behavior.
I jumped out of the truck, ran toward the bee cloud, and met them in front of the hives at the south end of the hive row. Immediately I had entered a diffuse, spread-out, barely humming, swarm. I knew I was inside a usurpation swarm. I have been inside these usurpation swarms before. The delicate “feel” was the same (see Figure 2), nothing like the roaring buzz of a large spring reproduction swarm (see Figure 3).
Technically, at this point, being careful, it is more proper to consider the swarm as potentially a usurpation swarm because it could cluster under a hive entrance (a suspicious location) and then just leave the apiary (which has occurred even here). So while this behavior (entering the apiary) was highly suspicious for a swarm preparing to usurp a colony, it has not displayed that behavior yet. For me, the swarm is not a completely confirmed usurpation swarm until I see it rush through the entrance or I find evidence of it in the host hive (see below). Nevertheless for brevity, I will call the possible usurpation swarm, just a usurpation swarm, bearing in mind this reservation.
Ever since I witnessed a usurpation swarm rush through an entrance hole of a top-bar hive (on August 11, 2009), I have wanted to record that behavior in slow motion for a more detailed bee behavioral study, especially any visible mechanism(s) signaling the mass exodus into the host hive. (My slow motion would be about 240 fps, frames per second, which for this mass movement should be slow enough.)
The usurpation swarm was beginning to land on the horizontal supports running between my frame hives. Unfortunately for my documentation, when trying to take over a colony, a usurpation swarm must submit to the current conditions and the fortunes or failures inflicted by capricious chance. The swarm had considerable difficulty flying against a brisk headwind from the north. The wind kept pushing the bees back out of the apiary until I thought the bees might land somewhere in the deep weeds just south of the apiary. Then I would need to put on my snake guards (which wrap around my lower legs) and go search for the bees.
After recording and watching the bees for about ten minutes, they managed to fly past three hives (at the south end of the hive row). Clearly the usurpation swarm had no interest in those colonies. The usurpation bees landed beside the fourth hive, mostly on its left (south, leeward) side. The bees did not cluster the way a spring reproductive swarm does with festoons of bees. Rather, only a single layer of excited bees formed on the wooden support beside the hive. Compare the usurpation swarm landing by the frame hive in Figure 4 with a known usurpation reference swarm from August 11, 2009 shown in Figure 5.
In the top-bar-hive apiary in 2009, the weather was clear without wind or approaching rain, which the 2021 usurpation swarm in the frame-hive apiary had to endure. In the top-bar-hive apiary, the usurpation swarm gathered completely on the hive support before rushing into the hive. In the frame-hive apiary, the usurpation swarm landed initially on the side of the hive as well as the horizontal hive support. Landing on the vertical side of the hive may have been to shelter from the wind, blowing from the other side of the hive, or possibly it was just variation in the initial landing positions. With the 2009 top-bar hive, Figure 6 shows the invasion behavior I was expecting into the frame hive without the queen problem, the headwind, and threatening rain, as explained below.
The crucial problem for the 2021 usurpation swarm in the frame-hive apiary was their queen was not with the swarm. I could not find her either, even from a rapid diligent search from under the host hive, or looking around the hive row under the swarm’s flight path and extending on …