posted by Josh Evans
I recently met with an entomologist at Copenhagen University who specialises in apiculture and bee pathology, and it turns out that the reason beekeepers remove some of the drone brood early on in the season is not to enhance honey harvest (as I naïvely thought) but rather as a strategy to regulate the Varroa mite population in a hive. The larvae are an easy target for the mite, and the drones in particular attract the highest concentration of mites because of their extended developmental period, staying in the larval stage for a few days longer than worker bees. Once the queen lays the eggs in the comb, the individual hexagonal cells are sealed with wax until the larvae pupate and hatch – but not before the mites find their way into the cells too. Since the drones attract the greatest number of mites, beekeepers use drone brood as a sort of decoy, drawing the mites into the cells then removing the brood to keep overall mite levels low – they remove about one third of a hive frame per week during the season. This technique, called the 'safe strategy', was devised by the Danish Beekeeping Association (Danmarks Biavlerforening) as a way to contain Varroa mite populations without using chemical pesticides.
The mite harms the bee by biting holes in the bee's tissue which cannot heal, opening their circulatory system to the environment. It then serves as a vector for viruses to attack the weakened bee. So why do we eat the drone brood if it's covered with Varroa mite? In fact, the mite itself poses no threat to other organisms. The drones would almost all die anyway, so we are in some sense helping our apian friends by consuming the most serious threat to their population.
Thanks to Annette Bruun Jensen for the information. The story keeps getting better.