The monotone buzz of a busy bee traveling from blossom to blossom on a breezy spring day is recognizable to many and invokes feelings of warm weather and sunshine (or a threat to those who have no interest in getting stung). This familiar buzz is one of many noises that a honey bee can make depending on her activity in the hive. As any beekeeper knows, the bees will make a constant background hum as hive inspections are carried out. This general buzz of the bees is generated by the beating of their wings and abdomens as they carry out their daily activities. Scientists are unaware of any specific communication that is carried out with this type of buzzing. With certain circumstances, however, the bees can make more particular noises. For example, when we are checking to see if a hive on our campus apiary is queen-right, we can tell almost instantly if the queen is removed from the hive because the background hum turns to a louder, more agitated roaring noise. Even without any ears or “hearing” organs, honey bees emit a variety of particular noises to interact with other bees in the hive.
Without being able to “hear” as we humans understand, how exactly do bees communicate with the noises they make? The answer lies in sensory organs called chordotonal organs that all insects have. These organs allow them to sense vibrations and noises from the outside world. Although honey bees lack tympanal organs, one of the types of chordotonal organs that deal with hearing noises, they still possess two chordotonal organs: the Johnston’s organ and the subgenual organ. The Johnston’s organ (located in the bee’s antennae) helps to detect vibrations passed through air, like the beating of wings during the waggle dance. Bees use their subgenual organ (located in their leg/knee area) to sense vibrations passed through material that their legs touch (such as honeycomb). Both organs are clusters of nerve cells that take the vibrational stimuli and convert them to neural signals (Collison, 2016). The neural signals will then direct the bee to what is happening in the hive, whether it be the presence of a bountiful nectar source near the hive or the emergence of a new virgin queen, two events that are communicated by specific noises emitted by bees.
The two specific noises that the bees make when these two events happen are the buzz of the wiggles and beats during the waggle dance and the piping noises that queens generate. In the waggle dance, the vibrations that a bee makes are used to communicate with her fellow forager sisters in the hive. Each body wiggle and wing pulse of the waggle dance is calculated to exude a specific frequency that alert the honey bees of the direction and distance of a food source from the hive. These vibrational frequencies and their lengths are detected by the chordotonal organs of the bee’s hivemates, who can then choose to travel to the new nutritional source. The second specific noise that queens will emit is piping. Piping is a broader category of noises that consists of higher-frequency toots and lower-frequency quacks (Collison, 2018). It is caused when the bee contracts her flight muscles without unfolding her wings and presses her thorax to the honeycomb (Caron & Connor, 2013). Piping is often performed in short bursts of pulses. This is a rare noise used in the emergence and activity of virgin queens and in times of swarming. Virgins will utilize this noise to let the whole hive (along with any other virgins who might be present) know that she is present in the hive and means business. Adult, mated queens might also make piping noises, which are thought to alert the hive of departure timing in swarming.
For an earless hive, bees sure do make lots of noise!
References
Caron, D. M., & Connor, L. J. (2013). Honey bee biology and Beekeeping. Wicwas Press.
Collison, C. (2016, February 22). A closer look: Sound generation and hearing. Bee Culture .
Collison, C. (2018, July 18). A closer look: Piping, Tooting, Quacking. Bee Culture. https://www.beeculture.com/a-closer-look-piping-tooting-quacking/
Hunt, J.H. and F.-J. Richard (2013). Intracolony vibroacoustic communication in social insects. Insect. Soc. 60: 405-417.