Important points
- Bees are among the most important pollinators of flowering plants, and they pollinate a large share of crop and wild plants.
- Sex determination in honeybees depends on the haploid-diploid mechanism.
- A male bee (drone) develops when the egg (female gamete) is not fertilised. The haploid egg divides by mitosis to produce fertile males with a haploid body, by a process called parthenogenesis.
- A female develops when the egg is fertilised by the male gamete (sperm).
- There are two types of females in a bee colony, i.e. the sterile female (worker) and the fertile female (queen).
Haploid-diploid mechanism of sex determination
In honeybees, the sex of an individual depends on the number of sets of chromosomes it receives. This is an exception to the usual sex-chromosome-based mechanisms (like XX-XY), as there are no sex chromosomes.
Unfertilised egg
Egg (n = 16) → divides by mitosis (parthenogenesis) → Drone (n = 16) – fertile male
Fertilised egg
Egg (n = 16) + male gamete (n = 16) → Zygote (2n = 32) → female
Fed royal jelly → Queen bee (2n = 32) – fertile female
Not fed royal jelly → Worker bee (2n = 32) – sterile female
| Feature | Drone | Worker bee | Queen bee |
|---|---|---|---|
| Sex | Male | Female | Female |
| Develops from | Unfertilised egg (parthenogenesis) | Fertilised egg | Fertilised egg |
| Chromosome number | n = 16 (haploid) | 2n = 32 (diploid) | 2n = 32 (diploid) |
| Royal jelly | – | Not fed | Fed |
| Fertility | Fertile | Sterile | Fertile |
NCERT: in honeybees, an offspring formed from the union of a sperm and an egg develops as a female (queen or worker), and an unfertilised egg develops as a male (drone) by parthenogenesis. The males have half the number of chromosomes (haploid) and the females double. Because males are already haploid, drones produce sperm by mitosis, not meiosis.
A common NEET statement: in the haplodiploid system, a male (drone) has no father and thus cannot have sons, but he has a grandfather and can have grandsons. Whether a female becomes a queen or a worker depends on diet (royal jelly), not on her genes.