Honeybees use haplodiploid sex determination: fertilized (diploid, 2n) eggs become females — workers or queens — while unfertilized (haploid, n) eggs become drones. A drone has no father and cannot pass on a father's genes; every sperm cell he makes is a genetically identical copy of himself.
On her single mating flight a queen mates with roughly 10–20 drones from a drone congregation area, storing all their sperm for life. Each drone founds a distinct patriline — a subfamily of half-sisters sharing the queen as their mother but a different father. The comb in this scene tiles worker brood cells and colors each one by its patriline, so more mates visibly means more colors and more genetic diversity for the colony to draw on against disease and changing conditions.
Bee sex is set by a single csd gene locus: heterozygous diploid eggs become
female, but if a diploid egg is homozygous at that locus it develops into a
sterile, short-lived diploid male — and workers detect and eat that larva,
creating a "shot brood" pattern of empty cells. Homozygosity is far more likely when a
queen mates with a close relative (a brother, or a drone from a closely related line),
so the Drone relatedness slider directly drives up the fraction of empty cells.
Selective breeding programs choose queens whose colonies show a desired trait — such as Varroa-mite resistance (e.g. hygienic or "grooming" behaviour), calmer temperament, or higher honey yield — and requeen from those lines. The Selection pressure slider controls how strongly the next generation is drawn from trait-carrying colonies; each "Breed next generation" click nudges the population's average trait frequency toward the selected type, while polyandry keeps some diversity from being lost outright.
Because a drone is haploid, all his daughters (workers) automatically share his exact genome from him — full sisters within one patriline are related by 0.75, unusually close for animal siblings, which is one classic explanation for the evolution of eusociality.
A queen's single mating flight fixes the genetic makeup of her whole colony for years: this scene tiles worker brood cells by patriline, lets diploid-male losses appear as empty "shot brood," and simulates selective breeding for a chosen trait across generations.
Haplodiploid sex determination, why polyandry (mating with many drones) boosts colony genetic diversity, and how mating with related drones raises the diploid-male death rate via the single-locus csd sex gene.
Set how many drones the queen mated with and how related those drones are, pick a trait breeders are selecting for, set the selection pressure, then click "Breed next generation" and watch the trait-carrier fraction shift.
Because drones are haploid, every one of a drone's daughters gets an identical copy of his genome — full sisters within a single patriline share about 75% of their genes, unusually close for animal siblings.