EN The hypopharyngeal gland

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Contrary to what their name might suggest, the hypopharyngeal glands (symbolically also called “mammary glands”) are located in the head of bees (queen and workers), between the two compound eyes. They develop mainly in young worker bees aged between 6 and 15 days, the so-called nurse bees.

The two branches of this gland that produce royal jelly are each composed of around 500 glandular units (acini), arranged like small grape clusters. Gland development and royal jelly production depend on the presence of open brood (which secretes a stimulating pheromone) and on pollen intake. From about the 15th day after worker emergence, these glands atrophy without disappearing completely, and jelly production ceases—only to resume if required, for example when the queen restarts egg laying after winter. In cases of food shortage, persistent cold, prolonged rain, lack of incoming resources, or absence of open brood, the hypopharyngeal glands enter a forced resting state. These modulations are governed by epigenetic mechanisms mediated by vitellogenin, a key “youth hormone.” Exposure to pesticides during the larval stage prevents the normal development of the future nursing glands of the imago.

In addition to producing royal jelly, hypopharyngeal glands allow older workers, through trophallaxis, to metabolize sucrose (a disaccharide) contained in nectar. By secreting an enzyme (invertase), workers split sucrose into two simple sugars, fructose and glucose, which are then stored in the comb cells as honey.

Drones lack hypopharyngeal glands and are strictly dependent on nurse bees for their nourishment. In autumn, they are mercilessly starved by the workers and ultimately expelled from the hive.

For further reading:

► Royal jelly: one of the many factors in producing a queen
► DNA adaptation according to role