What is Arnhart's gland in the bee?
- A recall gland that workers expose at the hive entrance to orient the colony.
- A sting gland that releases mainly an alarm pheromone during a sting.
- A tarsal gland involved in depositing a footprint pheromone, particularly useful for orientation at the hive entrance.
- A tarsal gland whose secretion helps signal the presence of the queen in the colony.
Show answer
Correct answer: 3 + 4.
3. A tarsal gland involved in depositing a footprint pheromone, particularly useful for orientation at the hive entrance.
4. A tarsal gland whose secretion helps signal the presence of the queen in the colony.
Why?
Arnhart's gland is a tarsal gland, located on the legs. It produces a secretion linked to the adhesion of the legs and to depositing a chemical 'footprint' on the surfaces the bee walks over.
In the queen, this secretion is deposited as she walks over the combs. Together with other queen pheromones, it contributes to the workers' perception of the queen's presence.
In workers, tarsal secretions can also play a marking role in certain contexts, for example near the entrance or on visited surfaces. They should not, however, be confused with the Nasonov pheromone, which is involved in recall and collective orientation.
What to understand
The bee's chemical communication does not rely on a single gland or a single molecule. The presence of the queen, the organisation of the colony, orientation, and swarming depend on a set of combined signals.
Arnhart's gland is interesting above all because it links a very simple behaviour, walking on a surface, to a discreet chemical message. The queen thus leaves a trace of her passage on the combs, which adds to the information available to the workers.
In beekeeping practice, an overly mechanical conclusion of the type 'more footprint pheromone, therefore no queen cells' should be avoided. The building of queen cells also depends on colony strength, the age and quality of the queen, the space available, the season, and swarming dynamics.
Key takeaways
Arnhart's gland is a tarsal gland, associated with the bee's legs. It produces a secretion linked to adhesion and the chemical marking of surfaces.
It should not be confused with the Nasonov gland, which plays a major role in recall and collective orientation, nor with the glands linked to alarm or venom.
In the queen, the tarsal footprint pheromone helps signal her presence, but its effect is part of a broader set of queen pheromones.