To study the causal mechanisms underlying the control of egg sex by honeybee queens (Apis mellifera), the queens were allowed to lay eggs in experimental cages without comb cells. The sex of the eggs laid were then determined by counting the number of chromosomes, and by observation of female and male pronuclei in the eggs and sperm cells on the surface of the eggs. It was found that queens laid normally fertilized diploid eggs under the experimental conditions. These results suggested that honeybee queens lay fertilized eggs when no information of comb cell size is available, thus the idea that queens would be stimulated to release sperm by small worker cells fitting queen's abdomen is not supported.
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