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Drone surrounded by worker bees. © INRA, MORISON Nicolas

Scientists flying to the rescue of bees

Is the European honey bee too gentle for this harsh world?

Besides its high productivity, the European honey bee is characterised by its gentle nature. But some researchers think that this trait could place it at the mercy of certain invaders. Its Asiatic counterparts (Apis ceranae) know how to resist or fight against better than them; against the Nosema fungus, yellow-legged hornets or even Varroa destructor. Similarly, the aggressive African honey bee can repel the small hive beetle (Aethina tumida), against which the European honey bee is defenceless. Will the gentle bee of our regions learn to face up to these threats? This is perhaps happening now in some cases.

Updated on 03/24/2017
Published on 05/01/2014

Social immunity: bees can defend themselves

We all know about individual immunity, the body's ability to defend itself against pathogens. But social immunity is less well known. However, when faced with a threat, honey bees are able to modify their behaviour in order to protect the hive. For example, when nurse bees detect that a brood is infected by a parasite, they do not hesitate to expel the affected larvae from the hive. Some behaviours, which are almost sacrificial, are also considered as a form of social immunity. Thus the INRA research group in Avignon noted that young bees affected by parasites become foragers at a younger age and spend more time outside the hive; in this way, they become isolated and have less contact with their fellows, thus preventing the parasite from spreading within the colony.

Pharmacist bees

An infection declares itself in the hive? The bees do not remain unmoved. Foragers redouble their efforts to bring propolis back to the hive. This mixture of plant resins has strong antibacterial properties that have not gone unnoticed by honey bees.

Could the European honey bee stand up to Varroa?

And what might happen if bees learned by themselves to fight against Varroa, in the same way as their Asiatic cousins? This is perhaps what is now happening. When the mite started to invade France in 1982, almost all wild-type swarms perished. Then as from 1994, these wild swarms started to reappear. By studying them, INRA scientists discovered two bee populations that were resistant to Varroa: the life expectancy of their colonies exceeded 8 years, despite chronic infestation. How? Some were able to inhibit proliferation of the parasite, while others learned to eliminate infected cells. The researchers think that these bee populations, if appropriately bred, could constitute the source of a new population of healthy honey bees that know how to circumvent attacks from Varroa destructor.

Three self-defence techniques against yellow-legged hornets

Little by little, European honey bees are learning to counter-attack when they encounter yellow-legged hornets lying in wait for them in front of the hive. The first tactic is hand to hand combat: if the bee manages to attack first, it will kill its opponent, but will die in turn because it has lost its sting. The second tactic, which has also been observed in Asiatic bees, consists in collecting thirty or forty bees together to form a compact ball around the invader, which is rapidly asphyxiated. The third tactic is equally surprising: the bees place themselves side by side to form an animated line of undulating motion. This formation is notable for frightening the hornet, which then prefers to beat a retreat. Although still rare in Europe, these behaviours could gradually develop.