Column by Jürgen Tautz: Fragrant Clues: Geraniol Points the Way

Honeybees live in a world of scents. During the course of their evolution, flowering plants developed the bouquets that we humans find so attractive especially for the small pollinators, and above all for the honeybees


The significance of a bee’s sense of smell becomes quite evident when observing the insect directly: its feelers are packed full of ten thousand olfactory cells, which are extremely sensitive to scents. If we take a look inside a bee’s brain, the olfactory system is by far the most complex and voluminous element.

Thus, it comes as no surprise that such olfactory machinery is also used for the purpose of communication among the bees themselves. As a matter of fact, scents are used both inside and outside the hive as a means of orientation and communication.

Measuring scents in their spatio-temporal dynamics is difficult from a methodological standpoint, especially outdoors, which is why this field of research is still in its infancy.

One scent that is especially important for the purpose of orientation outdoors is geraniol. It is produced in a gland at the end of a bee’s abdomen, called the Nassanov gland. Bees open this gland while standing in place and generating an air current with their wings to show their hive-mates the way back to the hive entrance. At new nesting sites and feeding grounds, bees conduct sprinkler flights, which are audible for us humans, spreading geraniol for their hive-mates. 

An experiment demonstrated that the scent trail of geraniol is so alluring to the bees that they can be sidetracked while flying and led away by even a thin fishing line with its end dipped in geraniol. This is extremely useful for the bees, even if they have been roughly informed about a target region by means of the waggle dance in the hive, as they would get lost without any associated lure (Tautz & Sandeman, 2003). These types of simple experiments help us to understand what causes recruited bees from random search flights to abruptly arrive at their target via the right trail (Fig. 1). There, instead of landing on the flowers, they are even likely to land on the experienced bees releasing the geraniol into the air (Fig. 2).

Literature:

Tautz, J, Sandeman, DC: Recruitment of honeybees to non-scented food sources. 
Journal of Comparative Physiology A 189 (4), 293-300, 2003.

Menzel, R, Kirbach, A, Haass, W-D, Fischer, B, Fuchs, J, Koblofsky, M, Lehmann, K, Reiter, L, Meyer, H, Nguyen, H, Jones, S, Norton, P, Greggers, U: A Common Frame of Reference for Learned and Communicated Vectors in Honeybee Navigation. Current Biology 21, 645-650, 2011.