Plants attract bees with plenty of caffeine in the nectar

Bees are manipulated by substances in plants
Caffeine is said to make you alert and stimulating. These are two of the reasons why many people like to drink tea or coffee. But also honey bees seem to have a preference for the "watchmaker". Because plants attract the honey collectors with the stimulating substance in their nectar. The honey bees prefer caffeinated nectar to an equally nutritious source without caffeine. Thus, the insects are bound to a food source and in addition, the collection zeal of the bees is stimulated. The insects remain loyal to such plants for a particularly long time and some plants exploit the small weakness of the honey collectors for their own purposes.

Plants attract the bees with caffeine in the nectar. British and Swiss researchers found that bees prefer a caffeine-containing nectar source over an equally nutritious one without caffeine. The plant uses this weakness of honey collectors to get rid of "inferior goods". Roger Schürch, lead investigator, said plants use caffeine to drug the bees. It seems to the honey collectors, as if the nectar has a higher quality. Actually, bees are used to transport the pollen of the plants to other flowers. So a reproduction and better spread is possible. In compensation for their work, the small "pollinators" get nectar. This is a high-energy food source and is needed by the bees to produce honey. Now it seems that plants use caffeine to turn inferior nectar to the small honey collectors.

Caffeine attracts honey bees. (Image: Alekss / fotolia.com)

Caffeine: drug for bees
Caffeine occurs in low concentrations in the nectar of many flowering plants. In the journal "Current Biology" the researchers write that caffeine would be comparable to a drug. Bees consider a caffeinated food source to be higher in quality than it actually is. Some scientists have found in older studies that honeybees can cope better with the influence of caffeine. Thus, it is clear that the "awake-maker" has a special effect on the insects. Caffeine seems to activate the reward system in the brain. The researcher Jane Couvillon from the University of Sussex now wondered whether the natural behavior pattern of bees is influenced by caffeine.

Caffeine strongly influences the collecting behavior of bees
For their study, the researchers combined a sugar solution with caffeine. The dosage was as high as it would be in plants in their natural environment. It quickly became clear that caffeine stimulates the insects to more collecting activity. In addition, bees, which were under the influence of caffeine, brought their conspecifics increasingly to the affected food source. This happens through a so-called "tail dance" in the construction of the honey collector. At control diets with caffeine, the recruitment is quadrupled by the dance. The caffeine causes the bees to collect more of the nectar. In addition, they perform their dance more often, so more of the other honey collectors were informed about the caffeine-containing food plant. The bees remain loyal to such food sources for much longer. Although some of the sources had already dried up, the insects returned regularly. In addition, bees under the influence of caffeine rarely went in search of new food sources.

Use plant chemistry to manipulate pollinators?
It can be clearly seen that the effect of caffeine strongly influences the behavior of the honeybee. Both nectar behavior and the recruitment of other insects by the "waggle dance" are altered by the "awake-maker". A hive is bound by caffeine more strongly to such a source of food. The flock will always prefer a caffeine food source, even if the sugar content is actually lower than normal. The plants could now lower their sugar content, because the caffeine content still looks attractive and more collectors are lured. The hives would therefore have to accept high losses in their honey production, researchers found in a model calculation. Caffeine is not the only component of plants that affects bees and other insects. There are also various sugars, fragrances and minerals in nectar. The effects of these substances are not yet known and would need to be explored to see what their effect on insects is. It is likely that plants often use chemistry as a strategy to attract honey collectors and pollinators.