Washboarding bees

A mysterious behaviour of bees that remains unexplained to this day

One sweltering August morning I was going from hive to hive to assess the general condition of the bees. Besides the extent of the brood, I was also checking the pollen and the winter stores. As I moved from one colony to the next, I suddenly caught a strange movement out of the corner of my eye on the front wall of a nearby hive. More than a dozen bees had lined up in military order a few centimetres above the entrance. Facing the entrance, legs firmly planted, they were rocking their bodies back and forth, almost in the same rhythm. I knew at once that I might be witnessing a rare phenomenon, known in the Hungarian literature as “gyaluló méhek”, planing bees (in the international literature it is referred to as washboarding or rocking). Although to this day nobody knows exactly what triggers this behaviour, the phenomenon is so rare that many beekeepers never come across it in their entire career.

Rare as the sight is, the subject resurfaces from time to time in the literature and in the pages of beekeeping journals. Beekeepers, writers and researchers have tried to explain its cause with any number of theories, but none of them has yet been scientifically supported. In Hungary, Kálmán Sőtér was the first to describe the phenomenon, in his book A méh és világa (The bee and its world), in 1895. He filed the observation under a chapter titled “The games of bees”. In the 1950s Pál Zoltán Örösi put it this way in his book Méhek között (Among bees): bees washboarding at the entrance “lower their heads and rock their raised bodies back and forth. Its purpose is unknown.”

My own observations of washboarding bees

At the time of my observation the weather was dominated by a heat dome and a prolonged drought. The nectar sources had dried up and pollen collection had also dropped considerably, which made the brood fall off sharply. Of the 110 colonies at my apiary, this one alone showed the curious behaviour. It was otherwise a stronger-than-average colony, in a north-facing hive standing in the shade. The occupants of the hives right beside it, also facing north, behaved entirely normally.

The bees were “washboarding” not on the landing board, but a few centimetres above the entrance. This movement is clearly distinguishable from the orientation flights of young bees and from bearding in hot weather.

What is more, the rare sight did not pass from one day to the next. The colony kept washboarding for roughly two more weeks, though not every day. As the days went by, the number of individual bees washboarding steadily fell.

Past theories and refutations

Leafing through the old beekeeping press, it is clear that our predecessors, too, puzzled over this mystery a great deal and reached a range of conclusions. I describe a few of them below.

• The end of the flow: According to the notes of old Carniolan beekeepers and to articles in American beekeeping journals, washboarding is a sign that foraging has come to an end, when young bees are suddenly left without work.

• Weather forecasting: The skep beekeepers of Lüneburg believed that washboarding signals prolonged rain expected within a few weeks.

• Cleaning or rubbing: Some accounts say the bees are scraping off honey and pollen smeared on the entrance (Ferenc Páder, 1906), or trying to remove pollen stuck to their necks (Minderhoud, 1954). Huber and other Swiss and German researchers thought the bees were coating the wood with some kind of glandular secretion.

Later observations, however, called these assumptions into question one after another, and refuted most of them. Jordan, a researcher at the Vienna beekeeping institute, showed that washboarding is not tied to the flowering of any plant, nor to any particular season. Using colour-marked bees, he demonstrated that the same workers can repeat this curious movement on consecutive days.

In 1996, in the pages of Méhészet (Beekeeping), Jenő Suhayda drew attention to the fact that the bees sway on the spot, holding on with their bodies raised, and do not touch the wood with their mouthparts at all; so it can hardly be a matter of coating or scraping.

But what does a beekeeper’s gut feeling say?

Although we still have to wait for the final scientific verdict, what I have seen in my own apiary has set me thinking. Working from the weather and forage conditions and from the biology of the bees, I have tried, within my modest means, to interpret and make sense of what causes washboarding.

• Displacement activity of an “unemployed” generation? With no flow and the brood in decline, the 15–25-day-old young bees raised during the July flow may have found themselves in a social vacuum. With little to do inside the hive or out, it is conceivable that they were releasing the inner tension of idleness through this rhythmic displacement activity.

• Synchronisation and formation: Bees can pick up the vibrations of the wood through fine sensors on their legs. So it is conceivable that once the first worker began to rock, its neighbours simply took up the pattern of the vibration, then fell into a military row, until the synchronised movement emerged. This kind of physical feedback and attunement is nothing foreign to the closed, inner communication of a colony: think of the waggle dance, which bees use to tell one another about nectar sources.

• Why only one hive? Why this one colony, out of the 110 kept at the apiary, showed the phenomenon cannot be explained by a single cause. It is conceivable that the phenomenon arose from a chance meeting of a critical mass of young, unemployed bees and a particular genetic disposition.

The mystery remains

The cause of washboarding is still unknown. As in the time of Kálmán Sőtér and Pál Zoltán Örösi, in the age of modern research we have come no closer to knowing exactly what triggers this curious behaviour. To me, though, there is something reassuring in knowing that the closed world of the hive still holds secrets. Örösi’s words still hold, 70 years on: “Its purpose is unknown.”

Sources

Books

• Sőtér, Kálmán: A méh és világa (The bee and its world), vol. I. 1895, p. 872. — chapter “A méhek játékai” (The games of bees)
• Örösi, Pál Zoltán: Méhek között (Among bees) — chapter “Pillantás a kaptárba” (A look into the hive), subsection “A kijáróban” (At the entrance) (in every edition of the work)

Journal articles

• A „gyalulás”. (“Planing”) — press review after Die Biene 1968/3. Méhészet (Beekeeping), April 1968, p. 77.
• Gyaluló méhek. (Planing bees) — advice column, question 17. Méhészet (Beekeeping), May 1969, p. 93. (This article summarises the observations of François Huber, Johannes Mehring, Otto Morgenthaler, Karl Freudenstein, Ferenc Páder, Minderhoud and Jordan.)
• Gyaluló méhek. (Planing bees) — press review after American Bee Journal 1980/10. Méhészet (Beekeeping), March 1981, p. 55.
• Suhayda, Jenő: „Gyaluló” méhek. (“Planing” bees) Instructive observations column. Méhészet (Beekeeping), July 1996, p. 14.

Original sources cited in the 1969 summary

• Huber, François: Nouvelles observations, vol. II, 1814, p. 266.
• Mehring, Johannes: Bienenzeitung, 1866, p. 164, and 1867, p. 48.
• Oldendorf (on the weather forecasting of the Lüneburg skep beekeepers): Bienenzeitung, 1867, p. 48.
• Páder, Ferenc: Méhészeti Lapok, 1906, p. 11.
• Morgenthaler, Otto: Schweizerische Bienenzeitung, 1931, p. 210.
• Freudenstein, Karl: Biologisches Zentralblatt, 1932, p. 343.
• Minderhoud, lecture at the International Beekeeping Congress in Copenhagen, 1954
• Jordan, observations at the Vienna beekeeping institute