Drones are the underappreciated, but (in)dispensible gift in your hives. They are indispensible in that they are the key to keeping good genetic traits in your colonies and surrounding apiaries. They also seem dispensable, since we humans think that there are always more than we need, and culling the larvae is such a valuable tool for integrated pest management.
Varroa mites are more attracted to reproduce in drone larvae, and since drones take three days longer than workers to emerge from their cells, more reproductively mature mites are the result. The foundress mite picks up on the signals from the larval bee asking to be capped, and she hides in the jelly at the bottom of the cell until capping is complete. Any time after the cell is capped, and before the bee emerges, the frame can be frozen to kill both the supposedly worthless drones and the decidedly dangerous mites. Drone culling, also called drone trapping, is a very effective tool for reducing mite concentrations in the hive.
We need a lot more good drones
The popular thinking that we don’t need so many drones may not be quite right. Each drone congregation area (DCA) can have thousands of drones,1 and there may be many DCAs within flight range of your princess, who needs to mate with up to 50 hopefully unrelated males within her 15-30-minute flight. Unrelatedness of the drones to each other (not to mention to the queen) is an important factor in the future health of the colony the queen will head, since multiple genetic lines mean different immunities or weaknesses, as well as different behavioral strengths (i.e., pollen hoarding and propolis gathering).
It is also due to this mixing of drones from many colonies and the extreme polyandry (multiple matings) of the queens that good genetics such as varroa sensitive hygiene (VSH) can get washed out in just a few generations. Beekeepers test their colonies and rear new queens from the mother queens they like the best. Each beekeeper has a different list of traits that they find most desirable. But, rather than using this information only to help decide from which colonies to raise new queens, it should also have great bearing on which colonies are allowed to raise drones.
Drone genetics are key to healthy hives — as much as, or more than, queen genetics. In a perfect world, all of the drones in a DCA would carry mite-resistant traits, whether true VSH, ankle biting, auto- and allo-grooming (grooming themselves or others), or other methods bees use to control mite numbers, many of which probably remain unknown. Each of those drones would also contribute other good genetic qualities such as disease resistance, gentleness, high honey production, winter frugality, etc. Good genetic diversity, versus genetic bottlenecking, is important …
