The presence or absence of queens in colonies of the African honey bee (Apis mellifera scutellata) plays a critical role in determining whether invading workers of the parasitic Cape honey bee (Apis mellifera capensis) species are able to reproduce and dominate the colony, causing its eventual collapse, according to a study in Scientific Reports.

Cape honey bee workers do not reproduce in the presence of their own queen, but invade colonies of the African honey bee, where they develop into false queens (clones) and take over the host queen’s reproductive function. However, the presence of an African honey bee queen can inhibit Cape honey bee workers from becoming reproductively dominant via pheromone signals that deactivate their ovaries.

Fiona Mumoki and colleagues analysed ovarian activation and pheromone profiles in Cape honey bee workers collected from African honey bee colonies with and without queens (queenright and queenless colonies, respectively). They found that all Cape honey bee workers collected from queenless colonies had activated ovaries, whereas only 10% of workers from queenright colonies did. Cape honey bee workers collected from queenright colonies also had different, more worker-like pheromone profiles than workers from queenless colonies, which had more queen-like profiles.

The findings suggest that given the right colony conditions, African honey bee queens can prevent reproductive takeover and colony loss by influencing the pheromone profile and reproductive ability of the invading workers.