Individual intelligence of the honey bee

Measuring about 1 mm³, the bee’s brain is capable of remarkable feats thanks to highly sophisticated cognitive mechanisms. The bee makes decisions, memorises flight paths by precisely tracking the course of the sun, identifies food sources and evaluates them both qualitatively and quantitatively, and transmits multiple types of information to its nestmates in order to recruit a large number of foragers with differentiated skills.

Image above: Structure of the olfactory pathway in the bee’s brain (Menzel and Giurfa, 2001). LA: antennal lobe; GSO: suboesophageal ganglion; CP: pedunculate body; CM: median calyx; CL: lateral calyx; Pe: peduncle; alpha: alpha lobe; beta: beta lobe; LPL: lateral protocerebrum; CC: central body; OC: ocellus; optic lobe: LO: lobula; ME: medulla.

The bee is endowed with a “mini-brain” of one cubic millimetre, composed of approximately 960,000 neurons, i.e. about 100,000 times fewer than the human brain, which contains around one hundred billion neurons. It is structured into optic lobes, antennal lobes (the antennae enabling the bee to perceive odours, temperatures, CO₂ and oxygen levels, and air vibrations) and mushroom bodies, which are involved in memory and information processing—since the bee is capable of making choices by comparing elements drawn from its memory with those immediately before it. Thus, despite its small size, it possesses a whole range of cognitive mechanisms, which are essential in particular for foraging.

A bee of about one centimetre can indeed forage within a radius of three kilometres, i.e. some 300,000 times its body length. This requires considerable energy and the ability to orient itself in space: the bee flies about two metres above the ground; it can fly higher, but then needs landmarks in order to return to its hive. In other words, it must memorise a route, as well as the locations of the attractive food sources it discovers. It actively seeks out and identifies the most rewarding sources, memorises their position, and then summons its sisters to them through the dance process discovered by Karl von Frisch.

A bee therefore does not fly at random to a rose, a daisy or a carnation: having found a field of rapeseed, it is able to assess the sugar content of the nectar, to evaluate the size of the field, and it will recruit all the more nestmates the more attractive the rapeseed field is. All this is made possible by the internal navigation tools at its disposal, first and foremost a “compass” that takes the form of a filter.

The eyes of bees are indeed equipped with analysers (similar to polarising filters that filter the sun’s rays). Even when they can see only a narrow patch of blue sky, these filters enable them to identify the direction of the sun at all times. These large eyes are composed of a multitude of ommatidia sensitive to the polarisation of light, that is, to the plane of vibration of the sun’s rays: some perceive the sky as illuminated, others as dark, depending on this vibration plane. From the pattern of brighter and darker areas, the bee always knows where the sun is located. This compass, however, also represents a trap, insofar as the sun is not a stable landmark across hours and seasons. Consequently, the bee is capable of time compensation: numerous studies show that it possesses a kind of innate scheme indicating that in the afternoon the sun lies in the opposite direction to that of the morning, and vice versa. This scheme is refined during the bee’s first flights, which beekeepers readily observe on fine sunny days, when young bees take off, fly in all directions and spiral upwards into the sky: these are orientation flights during which they experience both the sun’s trajectory and their immediate environment.

The compass is not the bee’s only navigational tool; it also possesses a genuine “map”: it identifies elements of the landscape and can relate the directions of the sun to the distances and orientations of the surrounding landscape features. This is demonstrated by a very simple experiment: bees are placed in a given environment and allowed to orient themselves; they are then transported on an overcast day to a similar environment that is oriented differently. It is observed that the bee orients itself correctly only when the sun breaks through, because it then detects that the direction of the sun has changed relative to the landscape of the previous day. It therefore needs to link landscape elements with the course of the sun, since it indicates the direction of a food source relative to the sun—and its sisters, like itself, must be able to find this direction even when the sky is overcast.

How, then, does the bee manage to orient itself—or rather, to maintain a steady direction—given that it flies in a zigzag pattern (a necessity imposed by the many obstacles inevitably present along its route at just two metres above the ground)? It can be shown that if the path consists of a series of vectors—for example, leaving the hive, skirting a clump of trees and heading towards the food source—the bee indicates to its sisters, through the dance, the straight-line direction, abstracting from the various zigzags. In other words, it has computed distances and directions and knows exactly where it is in relation to its hive.

This ability to compute distances is demonstrated by what might be called the “deceptive tunnel” experiment, in which the bee must fly very close to the walls while a “false landscape” passes beneath it—essentially a random pattern designed to provide the bee with an optic flow comparable to that experienced when flying over a much longer landscape than the tunnel actually is. As revealed by the dance, the bee believes it has travelled a much longer distance than it actually has. This shows that the bee has knowledge of the distances it travels by examining the progression of objects beneath it, in a manner akin to an “optical reader”.

The bee is also capable of “proto-counting”, as shown by a simple experiment: pergolas are arranged at regular intervals, and a feeder is placed behind the third one. After the bees have become accustomed to the setup, the pergolas are moved closer together overnight, so that the feeder ends up behind the fourth. Some bees have correctly apprehended the distance and fly directly to the feeder; another group—about a quarter—flies to the third pergola. These bees were therefore orienting themselves not by distance, but by the number of pergolas. The experiment thus teaches us that the bee is capable of a form of counting, albeit a rudimentary one, and also that not all bees orient themselves in the same way: they use different skills to reach the same goal, demonstrating that they are not mere mechanisms executing innate “programmes”, but individuals with differentiated competencies and qualities.

Janine Kievits, “Individual intelligence of the bee”, Labyrinthe, 40 | 2013, 43–45.

> https://journals.openedition.org/labyrinthe/4308

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Individual intelligence of the honey bee

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