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  • Writer's pictureDave Black

From White Noise to Mite Noise

As a green and innocent young beekeeper (I was 34, pretty young then judging by all those around me) my tutors always impressed on me the value of using ‘eyes and ears’; simple observation. Looking was too easy, but it was a long time before I thought about listening to my bees, or at least a long time before the significance of the noise I couldn’t help but hear began to dawn on me.

The Apiductor, invented by Edward Woods in the 1950s for listening in to beehives as a form of swarm warning. The device didn’t take off globally, but the use of devices to predict hive states is becoming increasingly common explains Dave Black.

Other people had been at it for a lot longer of course, and their ears were like a wine sommelier’s nose, but tuned to the buzz, trills, toots, and quacks that narrate the lives of the hives. One such was a local-ish man who had died while I was still at school, but who remained a legend in British and American beekeeping minds – Eddie Woods. Eddie lived in Hinchley Wood, a small suburb I passed through every day in later years on my London train commute, about when I began my beekeeping journey.

Edward Farrington Woods MBE was an electrical engineer who joined the BBC in 1932 as a sound engineer. Amongst other things, he worked to produce the King’s Christmas Day broadcast and became known as ‘that nice Mr Woods’. During WWII when the country was digging for victory Eddie’s contribution was to take up beekeeping. Inevitably his mind turned to the sounds of the hive and in 1952 he patented the Woods Apidictor in the UK (Patent No GB2806082X 1952-10-31), and by 1957 had been granted a patent in the US too. It wasn’t until 1964 that small enough component parts became available to actually build it. Then he set to, eventually supplying and supporting about 200 units in Britain and another 100 or so abroad. Specifically, the Apidictor would tune you into swarming.

The Woods Apidictor, in the words of the Patent Office (to be read in best BBC received pronunciation…), “relates to the art of bee-keeping and has for its object to provide means for enabling the bee-keeper to obtain more accurate and definite information concerning the activities within a hive and the potential behaviour of its inmates than has been possible by the methods hitherto employed, but in a simpler and more economical manner, and with less disturbance to the bees…”

It consisted of a microphone to be inserted into the brood chamber through a hole in the back, a headset (a ‘Sethophone’) that would be worn beneath your veil, and a small box containing the electronics. The Apidictor had a three-position switch, and indicator lamp, and a volume control used to ‘tune’ your listening experience. Essentially, if the lamp went out on a ‘green’ volume setting – all good. If it was out on the yellow/amber setting watch out; if you were in the red range, ‘trouble t’ mill’.

Perhaps an idea before it’s time, the Woods Apidictors never really worked and faded away with disuse or neglect, but the idea that remote-sensing could work, and that sound might be a reasonable way to do it, has stayed with us.

So set your TARDIS Time Vortex Control, man the helm, and head for 2020! By now we are thinking beyond swarming, and trying to predict all sorts of hive states; disease, dysfunction, and disasters. ‘Precision apiculture’ is collecting continuous ‘vibro-acoustic information’ (not limited to audible frequencies) from accelerometers fixed to the combs, and looks for ‘signatures’ with clever machine-learning algorithms analysing the spectra.[i]

What does a beehive sound like? This graph, which displays data from Ferrari, Silva et als’ 2008 research Monitoring of swarming sounds in bee hives for early detection of the swarming period, illustrates the different in frequency (x) and amplitude (y) of a swarming sound (green), compared to a hive at night (blue) and during the day (red).

Does it work? Well, maybe, but it has produced some really interesting observations. For a not particularly surprising example, we can now be pretty sure that queen piping (‘toots’ and ‘quacks’) helps the worker population to co-ordinate the release of queens. By conveying information about how many queens are free or sealed the piping means that they can prevent the simultaneous emergence of rival queens. Only mobile queens ‘toot’. It has always been a bit surprising that such a large investment in reproductive females could be simply squandered in a fight. It also points out that beekeeping inspections can accidentally prompt the early release of a virgin queen so that more than one mobile queen is present within the hive. This is not a natural situation for the colony which is normally determined to manage an orderly release of virgins. And, as for clipped queens; chaos ensues.

In a more surprising example, the same study foundation has supplied a new observation about Varroa mites.[ii] Besides all the usual methods of mite monitoring some more ‘hands off’ techniques have been tried, including gas sensors for detecting signature odours, and video detection of mite presence, but these have the usual drawbacks, propolis and no light just to suggest two. However, it transpires that the ultra-sensitive but robust accelerometers used in the previous study are able to detect vibrations produced by a single individual mite. That the scientists can select this phenomena, described as a ‘jolt’ (like a spring or click), in a fully populated hive is remarkable.

It’s also remarkable that a mite is able to produce such a, relatively, strong signal and suggests that it must be an important functional signal for Varroa, otherwise why would they bother? They don’t just do it once but sometimes 100s of times and that represents a substantial use of energy for one thing. Naturally one question is, what is for? Another question might be, if we can use it for detecting mites, I’ll bet bees can too - do they? Are hygienic bees using their ‘nose’ to find mites, detecting chemical clues from the mite’s cuticle, or are they actually listening with their ‘ears’?

[i] Michael-Thomas Ramsey, Martin Bencsik, Michael Ian Newton, Maritza Reyes, Maryline Pioz, Didier Crauser, Noa Simon Delso & Yves Le Conte. The prediction of swarming in honeybee colonies using vibrational spectra. Scientific Reports, (2020) 10:9798 [ii] Harriet Hall, Martin Bencsik, Michael I. Newton, David Chandler, Gillian Prince, and Scott Dwyer, Varroa destructor mites regularly generate ultra-short, high magnitude vibrational pulses. Entomologia Generalis, (2021) DOI: 10.1127/entomologia/2021/1407


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