Varroa destructor mites need a capped brood cell to reproduce, and they strongly prefer drone brood over worker brood: drone larvae emit stronger feeding-stage kairomones and stay capped for about 14–15 days versus 11–12 for workers, giving invading mites extra time to produce more daughter mites per cell. Beekeepers exploit this bias by giving the colony a frame of drone-sized foundation (or a drone-sized comb frame), letting the queen fill it and the mites concentrate in it, then cutting it out and destroying it — sacrificing some drones to remove a disproportionate share of the colony's mites.
Because a single drone cell can host several times more mite offspring than a worker cell, regular drone-comb trapping can remove a large share of a colony's mite population over a season with no chemical treatment — a cornerstone biotechnical tactic in integrated pest management (IPM) programmes.
A 3D hive comb where Varroa mites concentrate preferentially in larger, longer-capped drone cells; cutting out and destroying that trap comb on a schedule removes a disproportionate share of the colony's mites.
Mites choose cells based on relative attractiveness and available reproduction time. Drone cells stay capped roughly three days longer than worker cells, so mites entering them produce more daughter mites — concentrating the population where it can be physically removed.
Adjust the drone comb fraction and mite attraction bias to see mites concentrate on the larger comb, set a removal interval, then harvest the trap frame — watch it slide out and the trapped mites disappear from the colony's total load.
Removal intervals must beat the drone brood capping period (~14–15 days) — wait too long and the trapped mites simply emerge with the drones and rejoin the colony.