Honeybee Biology

The Key of B

It’s probably safe to say that many of us spend more time texting and sharing photos on our phone than talking. Paired with a text, a photo rounds out the story. In my photos, there is an album titled Nature Sounds. It’s mostly for me but I share my recordings with like-minded bio-nerds. There are recordings of spring peepers, the lilting song of the wood thrush, green frogs, cicadas, katydids, crickets, even waterfalls. Of course, I also have my share of honey bee recordings.

Listening to my bees especially in the dead of winter makes me smile. It also makes me wonder: what is the key of bee? You know, as in do-re-mi. Do foraging bees sing in a different note than bees in the hive? Does the queen make sounds? And just how is it done? Answering the first question was relatively easy. Phone in hand, I find my way to the piano and sit on its worn bench, running my fingers over the keys, remembering the notes. Right index finger touches down on middle C. “Always start with middle C,” I hear my first piano teacher Mrs. Trichle say. Before I strike a key, I listen to the bees’ note again. I softly press middle C. No, that’s not it. I work my way up, then down the scale, and find their voice at B, just below middle C. Unbelievably so. I play the B scale. So many flats! Then the G scale, which is so much easier with only an F#, followed by the G chords, major and minor. It comes back, this knowing without knowing, the equivalent of muscle memory. I try the C scale and its chords, then F and D. I come back to B and compare it to my recording again. Yup, the key of B.

I could make an educated guess that the sound bees make comes from their wingbeats, and that the frequency or speed of the wingbeat dictates the pitch. The larger the bee, the deeper the sound, or so it seems if one compares the sound of a honey bee to that of a bumble bee. Hmmm . . . not very scientific. I wanted names for the structures that emit the sounds, the equivalent of vocal cords located in our larynx that produce speech and singing. If we can change our soundwave frequency to sing, can bees and other insects carry a tune, or at least hum, with their vocal cord equivalents? I decided to do a little research.

It turns out they can, though the sound comes not only from their wings. Bear with me while the bio-nerd gets scientific. First, the frequency of sound waves is measured in Hertz, or cycles per second. Think of it as the length between wave crests. A deep ocean wave’s frequency is about 20 seconds; that is, one wave takes 20 seconds to cycle from crest to crest. The frequency of sound waves is much higher, or maybe faster is an easier way to think of it. Middle C has a frequency of 261.626 Hz, meaning the wave cycles approximately 261 times per second. According to research, the hum of my bees when they’re in the hive has a frequency of 250 cycles per second. Pretty close to the frequency of B on the piano at 246.942. For reference, a typical human adult male voice has a frequency range of 85 to 180 Hz; an adult human female has a frequency range of about 165 to 255 Hz.

Beekeepers know that there is more than one frequency in a hive, depending on the circumstances. Any beekeeper who has worked with bees when they’re guarding their honey stores, or snapped stubborn propolis with a loud crack while lifting a cover knows the pitch of an agitated hive changes ominously.

But just how do they make these sounds? The short story is that they vibrate their wings though it’s a bit more complicated than that. One theory is that bees make sounds by ejecting air through spiracles, openings on the side of the thorax that are used for air exchange. Another possibility is that the bee vibrates its wings and the sclerites (hard plates) at their base, or maybe even the entire surface of the upper part of its body.

Bees make other sounds too. Once a month or so in winter I go out and give the hive a sharp rap on its side, my ear pressed up against the cold wood. What I hear tells me they’re alive and well. It’s a short burst of sound, made by workers in guard mode rocking forward on their legs in unison, producing a loud sharp buzz. This is followed by a “piping” sound, which almost sounds like a cat meowing. The queen can be pretty vocal too, piping, “tooting,” and “quacking” as she moves about the colony. A virgin queen will make piping sounds especially during swarm buildup so workers know which queen will stay with the colony as the old queen departs. You can hear it here, https://www.youtube.com/watch?v=AYecvVhkpKI. It seems there’s more to royal communication than pheromones.

The next question is why? The most common reason bees hum in the key of B is for ventilation of the hive. It can get awfully warm in there, even on a 35 degree day. Worker bees will gather on parts of the hive and create air currents by beating their wings. The sound produced has a basic frequency of 250 Hz. This also helps to circulate pheromones, broadcasting the status of the hive.

The one sound I do not have on my phone is the annoying sound of a mosquito. Yet it turns out there are some interesting things about even these blood-thirsty creatures. Like bees, their sound is made by wingbeats but also aided by a toothed organ at the base of the wings, described as a “stridulating organ” by British entomologists way back in 1902. Both males and females make the distinctive high-pitched whine but we don’t often hear the male because he is not zeroing in on us for a meal. And the one redeeming fact about mosquitoes is the males are pollinators. Move over worker female bees and make room for the male mosquitoes on those blossoms.

The insect world is an orchestra of sounds, honey bees and bumble bees humming while crickets and cicadas keep rhythm. Go have a listen some summer morning.